2000 Vw Jetta Tdi Maf Reading at Idle

Dan Ferrell writes near practise-it-yourself car maintenance and repair. He has certifications in automation and command applied science.

You might be thinking of installing a new mass airflow (MAF) sensor to run across if it'll fix your engine driveability bug. But it's not a good diagnostic approach to just replace the sensor without investigating. Y'all can spend $100 or more than on a quality airflow sensor and yet solve nada. Only you lot can learn how to troubleshoot a MAF sensor in a few steps following this unproblematic guide.

Here, yous'll see:

• the most mutual problem affecting MAF sensors (and what to practice most it),
• how to find out whether you are dealing with a bad sensor,
• and what you need to pay attention to during your troubleshooting process.

Topics in This Article

1. Symptoms of a Bad MAF Sensor

2. How the MAF Operates

three. Troubleshooting a Mass Airflow Sensor

• A) How to Test the MAF Circuit for Power and Ground Signals
• B) How to Test the MAF Sensing Chemical element for Continuity
• C) How to Exam MAF Sensor Voltage Signals

4. MAF Sensor Test Results

v. How to Install a New MAF Sensor

i. Symptoms of a Bad MAF Sensor

You lot may have a bad MAF sensor if you find one or more of the post-obit symptoms:

• A decrease in engine power
• The engine vibrates (poor idling)
• The engine hesitates or stalls at acceleration
• More frequent stops at the gas station
• The engine surges at idling
• Other driveability problems
• Y'all go diagnostic trouble codes pointing to the MAF sensor

On some vehicle models, the MAF sensor likewise informs the calculator nigh air intake temperature and engine load (to control some automatic transmission functions). And so a bad MAF sensor on these cars can cause an even wider range of symptoms.

Yous can hardly diagnose a MAF sensor on symptoms alone. Other faulty components, like the fuel pump, fuel pressure regulator, and vacuum arrangement, can create similar symptoms. That's why you need to troubleshoot the MAF sensor (and related circuits as needed) before replacing components.

2. How the MAF Works

Before we spring into the diagnostic, allow's take a look at how the MAF sensor works so the process makes sense to yous.

Basically, the MAF sensor measures the amount of air flowing into the engine through the air cleaner assembly, which contains the air filter and connects to the throttle trunk.

Depending on the brand and model, your motorcar uses either a hot-wire airflow meter (the about common) or a hot-film blazon. Unlike design, same function: it tells the figurer how much air is flowing into the engine. The computer uses this information, along with input from other sensors, to provide the correct amount of fuel to the engine at any given time.

The hot-wire type sensor maintains a wire (located in the middle of the airstream) at a higher temperature than the air flowing in. To maintain this predetermined temperature, electric current to the wire increases as airflow increases.

In general, the hot-moving picture type sensor works the same fashion except it uses a movie instead of a wire to send the signal to the computer.

It is this actress corporeality of current the sensor is using that tells the estimator how much air is flowing in. In other words, the faster you drive, the college the cooling effect on the hot wire or moving-picture show, and so the more current flowing to the sensing element.

So you tin use the sensor operating logic to conduct your tests.

Here, we'll go over the steps you need to troubleshoot a hot-wire type MAF sensor using a digital multimeter (DMM) to read the voltage signals. Testing a film-type sensor is no unlike, except that you check for frequency signals instead of voltage. For this, you'll demand a digital multimeter (DMM) or an oscilloscope that can read frequencies. Other than that, the next steps apply.

Read More from AxleAddict

Use a DMM with at least 10 Megaohm of impedance.

Photo courtesy of Alper Çuğun on Flickr.

3. Troubleshooting a Mass Airflow Sensor

Now that you have a wide knowledge of how an airflow meter works, you are ready to test the MAF sensor. Let'south get set up.

1. Kickoff, open up the hood of your vehicle and locate the MAF sensor on the air cleaner assembly. Ordinarily, yous'll detect it between the air filter housing and throttle body. This could exist a small cake or a cylindrical department mounted as part of the air duct. On some models, you'll observe it inside the filter housing.
2. Look for an electrical connector on the air duct correct after the air filter housing. If you have difficulty locating the sensor, look it up in the vehicle repair transmission for your particular vehicle make and model.
3. To test the MAF sensor, yous'll need to have the electrical connector plugged in to the sensor. And so check if you can backprobe the wires. If not, you'll demand to pierce the wires using a pin when conducting your tests. If you lot use the later method, wrap the pierced wires with electrical tape when you lot're done with the tests, to preclude rust from creeping into the wires.
4. Identify the ability, ground(south), and signal wires on the electrical connector. Check your repair manual, ask at your local auto parts store, or search online for this information. Sometimes, yous tin can identify these wires by testing them as described afterward. So even if you don't have this information at hand, go ahead with the tests anyway.

Now, nosotros'll look at the steps to test a hot-wire type MAF sensor using a digital multimeter past reading its voltage signals. Remember that testing a hot-moving picture type sensor is basically the same except yous are reading frequency (Hz) signals rather than voltage. If y'all don't know what type of sensor you have on your vehicle, consult your vehicle repair manual, ask at your local auto parts store, or search online for the MAF sensor for your particular vehicle make and model and read through the description.

Caution - Tin Yous Crusade Electrical Damage With Your DMM?

Yes, you lot can. When troubleshooting electronic automobile components with a digital multimeter, always apply i with at least 10 Megaohm impedance protection. This prevents the meter from drawing too much current and destroying sensitive electronic devices.

A) How to Examination the MAF Circuit for Power and Basis Signals

Here, you check that your car computer is actually sending power to the airflow meter and grounding the circuit.

1. Unplug the MAF electrical connector. Visually inspect the electric connector and final for dirt or damage. Gently pull on the wires to check for tightness. A muddy, burnt, contaminated, or loose wire will interfere with the sensor signals.
2. Set your digital meter at or close to 20 Volts DC (direct current).
3. Connect your meter's red probe to the connector power final (on the side going to the computer) and the meter's black probe to ground (this could be on the engine cake, an unpainted bracket or the negative (black) terminal on your machine battery).
4. Plow the ignition key to the ON position, merely don't get-go the engine.
5. Your meter should read between 10 and 13 volts, close to battery voltage. If not, yous may take a fault in that part of the circuit between the electrical connector and the motorcar computer.
6. Now, connect your meter's blackness probe to the basis on the connector concluding (on the side going to the computer) and the meter's cherry-red probe to the bombardment'south positive (+) last.
7. Your meter should read between 10 and 13 volts, close to battery voltage. If not, you may have a fault in that function of the excursion between the electrical connector and the car estimator.
8. Plough off the ignition key.

B) How to Test the MAF Sensing Element for Continuity

1. At present, identify the terminals on the MAF sensor itself that stand for to the signal wire and ground.
2. Ready your meter to "continuity" or the lowest setting on the Ohms scale.
3. Connect one meter probe to signal and the other probe to basis on the MAF electric connector; polarity doesn't matter here.
4. You should read 0 (or close to 0) Ohms of resistance. If your meter reads infinite resistance, probably the MAF sensing element is burnt or broken. Visually inspect the sensor.

C) How to Test the MAF Sensor Voltage Signals

1. Plug the MAF electrical connector dorsum in.
2. Set your meter at or close to x V DC.
3. Commencement the engine and allow it idle.
4. Backprobe the betoken and ground wires (reddish probe to point and black probe to footing).
5. Depending on your MAF sensor, your voltage reading should exist between 0.threescore to 0.80 volts at idle. If your reading indicates 12 volts or pretty close to it, yous are probing the power wire, not the signal wire).
6. Increment engine speed between two,500 and three,500 RPMs by manually opening the throttle plate, or ask an assistant to depress the accelerator pedal. Your voltage should increase to about one.5 to 3.0 volts. Call up that increasing the engine speed increases airflow.
7. On a piece of paper, jot downward your voltage readings. Too, note whether the signal jumped, skipped, responded slowly to increased engine speed, or responded rapidly and smoothly. Head over to the Results sections below.

A bad MAF sensor may cause the engine to stall.

Photo courtesy of Konz Ortiz Luis on Flickr.

four. Interpreting the Results of Your MAF Sensor Test

Now, compare the results of your voltage (or frequency) readings to the specifications in your vehicle repair manual.

If the MAF Sensor Responds Slowly or Not at All

Commonly, a slow response, or no response, from the MAF sensor means ane of iii things:

• The MAF sensor has failed.
• The hot wire or film element is dirty or damaged and then that it is unable to 'experience' air menstruum.
• The sensor cocky-cleaning electrical circuit (on hot-wire types) has failed.

The about common cause of MAF sensor failure is a dirty sensing element.

Depending on your specific results, you may desire to check the sensor itself:

1. Disconnect the MAF sensor from the air cleaner assembly and visually audit the sensing chemical element.
2. If the sensing element is dirty, the sensor might really be working only contamination is preventing it from doing its job.

Hot-wire blazon sensors have a self-cleaning electrical excursion that heats the sensing chemical element upwards to grand C degrees (1832 F) when you shut off the engine. If that office of the circuit fails (not uncommon), the sensor will end up covered in dirt and eventually neglect to read incoming air. A quick check is to take a look at the circuit fuse and so test the relay that controls the cocky-cleaning circuit. Use this guide How to Test a Fuel Pump Relay and Other Automotive Relays to check the relay in the excursion. If necessary, consult your vehicle repair manual to locate the relay.

As well, you may want to try cleaning the sensing element with MAF sensor cleaning spray. Avert touching the sensing chemical element, and never make clean a sensing element with a rag or cleaners not intended for a MAF sensor or electrical contacts. Follow the product manufacturer instructions, and retest the MAF sensor following the previous steps.

If Cleaning the MAF Sensor Solves the Problem

If cleaning the MAF sensor with the cleaning solution solves the problem, and then:

• Yous may have a problem with the self-cleaning circuit
• An air leak effectually the cleaning associates is bypassing the air filter.
• A depression-quality filter is shedding textile and sticking to the sensing chemical element.
• An air leak effectually the air filter housing (a fissure on the filter housing or improperly installed filter cover or loose clamps) is introducing unfiltered air and contaminating the sensing element.

If Your Tests Don't Find Anything Wrong With the MAF Sensor

If your tests didn't reveal something wrong with the sensor or the circuit, but your computer says at that place's something wrong with it, check the role of the air cleaner assembly between the sensor and the throttle torso. Air leaks will trick the computer into thinking the sensor has failed.

If Your Results Seem Inconclusive

If you don't know how to interpret your results, check with your dealer, or on online machine forums defended to your vehicle make and model for a possible technical service bulletin (TSB) related to your trouble. Technical issues with the pattern or materials used in the MAF sensor or circuit tin show up afterward miles of driving.

five. How to Install a New MAF Sensor

If your tests indicate a bad MAF sensor, you can replace it yourself in a few minutes. In nearly vehicle models, all you have to practice is:

• Disconnect the part of the air intake duct that connects to the MAF sensor.
• Carefully unplug the sensor electric connector.
• Unscrew 2 or more sensor mounting bolts.
• Remove the old sensor.
• Install the new one.

Further Investigation

Most of the time, your test results will lead you to the crusade of the problem in a few minutes. For example, if a sensor fails to respond to an incoming point, y'all know that the problem lies with the sensor itself.

Other times, the results may not take you lot too far, especially if you don't have much experience in machine repair. When this happens, you can visit ane or more forums defended to your specific vehicle make where you can communicate with other drivers that might've faced this same blazon of trouble.

If your tests prove that your MAF sensor works every bit expected, maybe you're dealing with a fuel, ignition, or vacuum-related problem.

Most of the time, though, yous'll be able to discover the cause of the problem, make the repair, and become your auto back on the road sooner than yous thought possible.

This article is authentic and true to the best of the author's knowledge. Content is for informational or amusement purposes only and does non substitute for personal counsel or professional person advice in business, financial, legal, or technical matters.

Questions & Answers

Question: It is truthful that if you unplug the MAF sensor and the engine is however running then the sensor is bad?

Answer: Removing the sensor helps to diagnose a bad sensor in some cases. For case, unplugging a bad IAC that is causing a surge in some models, it can change the idle, and then you lot know the solenoid is causing trouble. And some do the aforementioned if they are having bug with the MAF. The computer uses a default setting if it doesn't receive the signal. But it'south better to troubleshoot the sensor, y'all may have a bad connector or wire, before replacing information technology.

Question: If I forgot to disconnect the battery and I plugged the MAF, how I can remove the notification of the check engine?

Reply: Make certain the sensor is properly connected. Sometimes the lite will reset itself. An auto parts store can check the code(s) and reset the light for you.

Question: when I connect my connector, the automobile shuts off. When I unplug it, it stays on but won't drive that fast. What'south the trouble, the connector or sensor?

Answer: Almost probable, the MAF sensor is bad.

Question: I have a 2012 Chevy Malibu. Information technology will not start. I disconnected the mass air menstruation sensor, at present it acts like it wants to start. Could the mass airflow sensor exist the problem?

Answer: It's possible. Download problem codes and see if you get whatsoever. Faulty camshaft and crankshaft sensor produce the same symptom.

Question: What does it hateful when the MAF sensor on my 1996 Chevy Tahoe has 1.23 ohms of resistance?

Reply: Reading some resistance on the signal path in the sensor means there'due south some "interference" confronting the current. This may bespeak a damaged or partially burned element.

Question: Tin can I reuse bolts to mass air catamenia sensor when replacing it with a new 1?

Reply: Aye you tin, if they're adept.

Question: On 2009 Mazda CX-7 if MAF sensor has been replaced twice with OEM part and it fails the next morning. What should I expect for?

Reply: Troubleshoot the sensor and see if the sensor itself is failing. At that place could be a problem in the circuit, bad connector or loose wire. Also, check for a possible vacuum leak, specially between the sensor and throttle torso.

Question: My check engine light is on. I cleaned the MAF sensor and reset by unplugging the battery simply information technology came on again. The automobile is running normally. It continues to run even when I unplug the connexion to MAF sensor. What could be incorrect?

Answer: Try erasing the trouble code with a scanner tool. If the MAF sensor or its circuit is faulty, unplugging the sensor will cause the computer to run with pre-programmed parameter (estimate) until you fix or supplant the sensor with a good unit.

Question: I just put a new sensor on my Lexus 2001 es300, and when I bulldoze my car around the corner, information technology however dies out. What could it be?

Answer: It's hard to tell. If it only happens when turning around a corner, look for a loose wire (possibly an ignition system wire - under the dash?), or a fuel pump event. Check for problem codes and see if you find anything.

Question: Volition my car run if the mass airflow sensor is disconnected?

Reply: Information technology may run. If disconnecting the MAF sensor makes a possible engine problem go away, check the cam and cranks sensors and fuel pressure.

Question: I have replaced my MAF sensor 3 times. Last 1 is an Air conditioning Delco unit. Bold that the MAF sensor is working correctly and sending information to the ECM, could the ECM be malfunctioning and causing the betoken information to get distorted or misread? What else could cause outside ambient temps to be off?

Reply: There's a possibility that the ECM exist malfunctioning, but is not that common. If you changed the MAF because a DTC, check the input and output voltages (incoming and outgoing) from the sensor. The problem could be in the circuit itself, the connector or a wire.

Question: I installed a new MAF sensor, but the car won't even idle. What is the crusade?

Reply: If the car was idling with the old MAF sensor, disconnect the new sensor and check if the engine idles. If it does, either the new i is faulty or mayhap there's something wrong with the circuit.

Question: Do I have to disconnect the bombardment before the MAF sensor is replaced?

Answer: No. But make certain not to leave air leaks when putting back the air cleaner assembly or you'll create a error and cause bad engine performance.

Question: Isn't a mass airflow sensor supposed to have a sure resistance between the signal and the basis on the sensor itself? I go about 8.8k ohm on mine. What could cause that much resistance?

Answer: Information technology depends on your application--meet your vehicle repair manual. On some models, swinging the sensor'south plate menstruum should produce a smooth increase in resistance.

Question: I'k not getting enough voltage getting to MAF sensor. Whatsoever ideas?

Answer: If you are getting some voltage, there could be a bad connector or loose wire. Check the terminals for a loose wire or bad connexion.

Question: My mass air menstruum sensor on an 88 Camaro 2.8 reads 5-volt reference between signal and ground while running and unplugged, on the ECM side, at idle. Shouldn't the mass air flow sensor dictate the voltage going out to the ECM? While plugged in, there is erratic non-detectable voltage, on/off, on/off. My ground tests good, and I accept excellent battery voltage on ECM side of the harness. I go the aforementioned result with ii mass air flow sensors.

Answer: Check the connectors and wires for loose or damage issues.

Question: When I unplug my MAF sensor, car shakes for 1-2 seconds and and so starts normally. I try to drive it with the MAF sensor and unplugged it seems to operate like normal. 2009 BMW 525I 3.0L. I take a problem when it's cold. Information technology has a rough starting but after two minutes, when it gets warmer, it's good. What could be the problem with my automobile's MAF sensor?

Reply: This could be from a faulty sensor, an engine coolant temperature sensor, for instance. Download trouble codes from the computer memory, even if y'all don't see the engine low-cal coming on. There could be a pending code. Also, try cleaning the MAF sensor. This is a common issue. This postal service may help:

https://axleaddict.com/auto-repair/How-to-Clean-a-...

Question: What does it mean if, when back probing to exam for voltage indicate, the engine dies? Now, when turning the primal to showtime, only ability comes on and the starter does non crank. Do you accept any clues to where the starter relay is located on a 1991 Park Avenue?

Respond: Cheque the battery connections and make sure voltage is reaching the starter relay. You may desire to exercise a voltage drib on the starting system circuit. This other post may help:

https://axleaddict.com/machine-repair/Automotive-Volt...

I believe in your model the starter relay is located towards the firewall. Await to the left of the steering column. You'll see the relay.

Question: I have an A4 Audi sedan ane.viii. If I replace the airflow sensor with a new ane, exercise I have to diagnose the auto if I replace the new ane with the old 1 once more?

Reply: You might want to test the old sensor and come across if it really failed. Sometimes a chock-full air filter or air leak in the ductwork can make a good MAF await bad. You tin follow the procedure in the mail service or the one in your repair manual. It'due south not a difficult procedure.

Question: My Volvo V50 runs well merely then suddenly will lose power. Sometimes information technology helps to shake the MAF connector just non always. Is it definitely a problem with the contacts or it tin be something else?

Reply: Check the sensor element for contamination so troubleshoot it. Take a good look at the connectors and wires, possibly a loose wire that reconnects when yous shake it.

Question: I take Hyundai i20 diesel 1.4 variant. Recently, the check engine calorie-free appeared in ODO meter. And then I checked it with the OBD2 tool. I got the error code P0103, which indicates MAF sensor excursion high input. What solution will work?

Respond: Test the sensor itself, its voltage output and for a poor connection. These are the most common causes for this lawmaking.

Question: When I tested my MAF sensor with a DMM it read weird. The DC voltage was assault 20, which was closest to ten. Mine would become the MAF sensor and went upwards to ii.49 at idle very quickly. With the engine at 2500 to 3000 rpm, it was reading two.45 and it got to that rapidly. Does that mean information technology'due south bad?

Answer: Non necessarily. Check your codes and encounter if information technology indicates issues with the circuit. If your DMM has Hz frequency - normally you'll get about 30 Hz at idle and volition increase as y'all open the throttle.

Question: Do I have to reset my computer after replacing the mass air menses sensor and throttle trunk?

Respond: Not necessarily. Y'all may want to clear the codes, and there could be a reset/relearn procedure for the ECU. Consult your vehicle repair manual. If you don't have one, your local library may accept a re-create.

Question: Does the ability wire to the MAF have to be the same gauge?

Answer: Yep, don't use a smaller one.

Question: I am in Nigeria, and I need an AIRFLOW METER for a 1996 Nissan Maxima. Please, how tin can I get a practiced new one from a reputable part dealer?

Answer: Y'all can contact your nearest Nissan dealer and social club the part through the service section. That way you'll be certain you are installing an OEM part.

Question: I cleaned the MAF sensor with the cleaner. It ran a little better, but however crappily. Should I supplant my MAF sensor?

Respond: Double-check there are no air leaks between the MAF sensor and the throttle body. Air ducts should be properly connected and not damaged. An air or vacuum leak can confuse the estimator near air volume. If possible, examination the sensor before replacing it. Y'all want to brand sure yous are dealing with a faulty sensor.

Question: The signal from MAF is reading 2.49-2.51v at idle and accelerating upwardly to 2000-3000 rpm voltage, but not changing. Does this mean the MAF has failed?

Answer: Make clean the sensor with MAF sensor cleaner. It's possible the sensor is muddy and messing the scale.

Question: 1990 Mazda Miata has major take off issues. How practise I become about testing the MAD on the car?

Answer: The best style is to follow the process in the repair manual for your particular model. You may be able to discover a re-create in your local auto parts store or online.

Question: P0102 engine code, rough idle, crude acceleration. Replaced mass airflow and won't idle or run. What could be the problem?

Answer: The source for the code may point to different things like the MAF circuit or electrical connector or vacuum leaks. Unplug the MAF sensor and try starting the engine. If you lot find something dissimilar, the trouble may exist in the wiring. Check the excursion voltages using your repair manual. Besides, bank check for a vacuum leak, including the hose between the MAF sensor and the throttle body. Promise this helps.

Question: How practice you read airflow meter wires?

Answer: Employ a digital multimeter and follow the instructions in the 2nd section of this mail service.

Question: I got a 2006 Subaru Liberty that has no air sensor. How practice I get by this?

Respond: If the sensor is missing, have it installed.

Question: How can I fix the idle air command valve?

Answer: Usually you lot tin remove the valve and clean whatsoever buildup out of the valve and throttle body. If the valve itself is bad, supplant it.

Question: Recently tested my MAF sensor and every thing looks fine. The voltage increases as the RPM increase and decreases as the RPM decreases. But when knocking on the sensor, the car struggles to idle normal or some times dies. What seems to be the problem?

Answer: There could be a broken wire in the sensor'due south circuitry. If lightly tapping the sensor changes the idle, the sensor is likely bad.

Question: What would cause MAF sensor output voltage go negative at times?

Answer: Sometimes this type of negative output comes from a faulty sensor; cheque for possible awaiting trouble codes (no check engine lite) that might confirm this.

Question: Will a bad mass airflow sensor crusade your battery to die?

Respond: No. A dead dead battery is commonly caused by a faulty bombardment, bad alternator or circuit or a parasitic draw. This other post may help:

https://axleaddict.com/auto-repair/car-batterydrai...

Question: I have a '98 Nissan Maxima. I replaced the coil, cam sensor, crank sensors, fuel pump, MAF sensor. What'due south wrong?

Reply: Even if the bank check engine light is not on, download DTCs for possible pending codes. If you know yous are getting adept spark and proper fuel pressure, these other posts might help:

https://axleaddict.com/auto-repair/My-Engine-Creepo...

https://axleaddict.com/motorcar-repair/bad_starter_sym...

https://axleaddict.com/auto-repair/My-Car-Wont-Tur...

https://axleaddict.com/machine-repair/How-to-Apply-Volt...

Question: 2014 Ford F150 cranks just won't first; it seems similar an intermittent problem. No codes are being given. The computer was replaced and it happened again. It has been going on for the past week. I'm existence advised to replace the MAF and Fuel Module Assembly. I was told it is one or the other. Whatever thoughts?

Answer: This type of intermittent problem normally points to electrical faults. A sensor might not exist able to transport the correct signal when the mistake is there. Check the circuit (wires, connector, harness) for those sensors the estimator depends on to manage fuel, and ignition timing. This could be the camshaft and crankshaft position sensor:

https://axleaddict.com/auto-repair/How-to-Test-a-C...

throttle position sensor:

https://axleaddict.com/auto-repair/How-Do-Y'all-Know...

or ignition control module.

Check the MAF sensor and excursion, if necessary:

https://axleaddict.com/automobile-repair/How-to-Test-a-M...

Question: I added a new MAF to my Nissan Titan 2004. Everything came out cracking. The only problem I have now is that when I press the gas, the engine sounds similar it is releasing air from the acme. What could be the event?

Answer: At that place could be a vacuum leak, just this would make the engine run rough. Make sure the air ducts are properly connected, there might be some air being sucked when the throttle opens -- sort of like a bypass.

Question: Does the Scion Xb 2008 2.four liter have a Maf sensor fuse ?

Reply: Check under the ability box lid or the fuse box within the cabin. At that place should bespeak the circuit fuses.

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Source: https://axleaddict.com/auto-repair/How-to-Troubleshoot-a-Mass-Airflow-Sensor

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