Air intakeGeneric OBD-II codeUrgency: Garage soon
Code P0104: air flow meter (MAF): intermittent signal
P0104 means: mass or volume air flow circuit intermittent (air flow meter circuit).[1][2] The engine ECU has detected that the air flow meter (MAF sensor) signal is failing intermittently or erratically: it is not a constant fault, but an unstable signal that is sometimes valid and sometimes not, so the ECU does not receive reliable readings of the air entering the engine.[1][2][3][4]
What code P0104 means
The engine ECU has detected that the air flow meter (MAF sensor) signal is failing intermittently or erratically: it is not a constant fault, but an unstable signal that is sometimes valid and sometimes not, so the ECU does not receive reliable readings of the air entering the engine.[1][2][3][4]
Because the fault is intermittent, it may not be present when the car is checked. Ross-Tech puts the sensor's wiring and connections first (with a possible short circuit), and Autodoc also cites loose or corroded connections, as well as the sensor itself.[1][3]
It is a generic OBD-II code (it starts with P0), not specific to one make, so its definition is the same on any car; what changes from one engine to another is the most likely cause.[5]
Original definition (SAE J2012): Mass or Volume Air Flow Circuit Intermittent[1][2]
Causes of P0104
From most to least likely, according to the sources.
- 1Air flow meter wiring and connectors: loose or corroded connectors, damaged wires and possible short circuits.[1][3]
- 2Faulty, dirty or clogged air flow meter. On VW diesels sold in Europe around 1995–2002 (the wiki itself marks those dates with a question mark), Ross-Tech states that the sensor tended to lose performance gradually through dirt rather than fail suddenly.[1][3][4]
- 3Air leaks in the intake, before or after the air flow meter.[1][3]
- 4Problems with the sensor's electrical supply.[1]
- 5Clogged air filter or faulty throttle valve.[1]
- 6ECU fault, which is uncommon (Ross-Tech describes it as rare).[1][3]
Symptoms
- Engine warning light on in the instrument cluster.[1]Engine warning light: faults that cause it
- Noticeable loss of power when accelerating.[1][3]Less power: faults that cause it
- Rough idle: the engine runs unevenly or hesitates.[1]Vibrations: faults that cause it
- Jerking while driving, especially at low revs.[1]Jerking: faults that cause it
- Hard starting, or starting that takes longer than normal.[1]Hard to start: faults that cause it
- Noticeably higher fuel consumption.[1]Uses more fuel: faults that cause it
- Black smoke from the exhaust is possible.[1]Black smoke: faults that cause it
- The engine may switch to a limp-home mode, with less performance and higher consumption.[1]Limp mode: faults that cause it
How to diagnose P0104
In order: from the most likely and cheapest to check to the most expensive.
- 1Check the air flow meter connector and wiring (loose terminals, corrosion, damaged wires) and clean corroded contacts with contact cleaner spray.[1][3]
- 2Wiggle the wiring harness and the connector at several points and in different directions while watching the air flow meter reading on the diagnostic tool or a multimeter: if the reading cuts out or jumps, you have located the area of the fault. This is the technique given in Saab's workshop manual for its air flow meter codes.[6]
- 3Measure the sensor's electrical supply with a multimeter.[1]
- 4Check the air filter (replace it if it is clogged) and look for leaks in the intake duct between the filter and the throttle valve.[1][3]
- 5If the sensor is dirty, clean it with a cleaner made specifically for air flow meters and let it dry before refitting it; do not knock it or use solvents, because they can damage it permanently.[1][7]
- 6In the workshop, the air flow meter's output voltage can be analysed with an oscilloscope by snapping the throttle open quickly: according to Bosch, a smoother rise than normal compared with that of the throttle valve sensor indicates deterioration. On VW diesels of that era (around 1995–2002), Ross-Tech also suggests logging the air flow at full load in third gear, between 1,700 and 4,000 rpm.[3][7]
- 7If the fault cannot be repaired, replace the air flow meter; the ECU is only checked once everything above has been ruled out.[1][3]
Can I keep driving with P0104?
Garage soon
Autodoc allows short journeys but asks for it to be repaired soon: the engine may switch to a limp-home mode, with less performance and higher consumption. Ross-Tech, on the other hand, notes that there are probably no serious running faults (only a loss of power), so the sources do not entirely agree on the severity.[1][3]
Documented faults related to P0104
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Engine sensors: the most serious faults by engine and car
- High severityFrequency: Occasional2.0 DTI and 2.2 DTIVP44 injection pump and air mass meter failureGerman Wikipedia documents recurring failures of the Bosch VP44 injection pump and the air mass meter in the early years of this engine. An owner testimony for this engine describes the pump being replaced at 192,500 km, at a cost the owner calls «prohibitive».
- Medium severityFrequency: Common2.0 TDIClogged particulate filter or faulty pressure sensorThe 2.0 TDI's particulate filter clogs if the car mostly makes short journeys, because it never gets to regenerate; sometimes the fault is just the differential pressure sensor. Cleaning it costs around €200 and replacing it, €800 to €3,000.Repair (garage): €800–€3,000
- Medium severityFrequency: Common1.4 and 1.6 8vCrankshaft position sensor failure (TDC sensor)The crankshaft position sensor (capteur PMH, or TDC sensor) appears repeatedly in the reliability sources for the Clio II, the Kangoo I and the Dacia Logan I with this engine, with hard cold starting or stalling as the main symptoms. It is a cheap part, but the failure can leave you stranded.
- Medium severityFrequency: Common1.4 and 1.6 16vCrankshaft position sensor failureThe crankshaft position sensor (capteur PMH) appears repeatedly in the reliability sources for almost every generation with this engine, with hard cold starting, stalling or the car cutting out unexpectedly. It is a cheap part, but the failure can leave you stranded.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- High severityFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- High severityFrequency: OccasionalM264/M254Poorly tightened 48 V earth wiring in the mild-hybrid system (fire risk)Mercedes-Benz has issued several recalls (2022-2025) because the 12 V and 48 V earth connections of some cars with a 48 V system may be poorly tightened: resistance rises, the connection heats up and a fire cannot be ruled out. The official workshop checks them and repairs them if necessary in an hour or more.
- High severityFrequency: Occasional1.9 TDIUnit injector tappet wear and injector wiring damageOn the unit injector system, the tappets that operate the injectors can wear if the oil is not changed on time, and the injector wiring can be damaged by contact with oil, causing misfires or loss of power.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
Frequently asked questions
How does P0104 differ from P0100, P0101 and P0102?
P0104 refers to an unstable or intermittent signal: it comes and goes, whereas P0100 is the general air flow meter circuit fault, P0101 a range or performance problem with the measurement, and P0102 a signal lower than expected. With an intermittent fault it is best to suspect the wiring and connectors first: Ross-Tech puts them first, although Autodoc cites the sensor itself first.[1][3][4]
Can I drive with code P0104?
Autodoc allows short journeys, but recommends repairing it soon because the engine may enter a limp-home mode with less performance and higher consumption. Ross-Tech, for VWs, states that there are probably no serious faults, just a loss of power.[1][3]
How do you locate an intermittent air flow meter fault?
The usual approach is to start with the wiring and connectors: wiggle them at several points and in several directions while watching the air flow meter reading (a technique given in Saab's workshop manual for its air flow meter codes), clean the contacts and measure the sensor's supply with a multimeter (Autodoc). In the workshop, the signal can also be analysed with an oscilloscope (Bosch).[1][6][7]
Does P0104 mean the same on all makes?
The definition is the same: codes that start with P0 are generic codes of the standard, and technical databases classify it as a generic OBD-II code. What changes from one car to another is the most likely cause; Ross-Tech, for example, documents a gradual loss of performance through dirt on the air flow meter in VW diesels from around 1995–2002.[2][3][5]
Will I pass the MOT with code P0104?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[8]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- Código de avería P0104 - guía paso a paso para su diagnóstico y resoluciónAutodoc Club · Technical documentation · consulted 2 October 2026 · in Spanish
- P0104 — Mass or Volume Air flow Circuit IntermittentThe Automotive Technician (TaT) · Technical documentation · consulted 2 October 2026
- 16488/P0104/000260 - Mass Air Flow (MAF) (G70): IntermittentRoss-Tech Wiki · Technical documentation · consulted 2 October 2026
- Medidor de masa de aire (MAF): funciones, síntomasAutodoc Club · Technical documentation · published 13 October 2020 · consulted 2 October 2026 · in Spanish
- On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- Saab 9-3 (9400) 2001, Trionic T7: P0100 Mass Air Flow Circuit. No Signal.Saab WIS Online (manual de taller de Saab) · Technical documentation · consulted 2 October 2026
- Lambda and Air Mass Sensors: An aid to fault diagnosisBosch Aftermarket · Manufacturer · consulted 2 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish