The OBD2 code P0104 indicates a problem with the Mass Air Flow (MAF) sensor circuit, characterized by intermittent signals that disrupt the vehicle’s ability to accurately measure the air entering the engine.
This sensor is crucial for calculating the optimal fuel mixture by monitoring the amount of air intake. Intermittent faults can lead to various driveability issues, such as surging, rough running, and even stalling, as the engine computer struggles to maintain the correct air-fuel balance.
P0104 quick overview
| Meaning | P0104: Mass Air Flow (MAF) Sensor Circuit Intermittent |
| Is it serious? | Yes, because intermittent readings can lead to unpredictable engine performance, reduced fuel efficiency, and increased emissions. |
| Possible causes | – Dirty or faulty MAF sensor – Loose or damaged wiring and connectors – Air intake leaks affecting the sensor’s readings – Potential issues with the vehicle’s ECM (Electronic Control Module) |
| How to diagnose? | Inspect and clean the MAF sensor to remove any obstruction or debris. Check the air intake system for leaks that could alter airflow readings. Inspect the MAF sensor’s wiring and connectors for damage or poor connections. Use diagnostic tools to monitor the MAF sensor’s output and check for intermittent behavior. |
P0104 Meaning
Think of the MAF sensor as the lungs of your car, measuring how much air is breathed in to mix with the fuel for the perfect combustion recipe. When you get a P0104 code, it’s like those lungs are hiccuping, sending confusing signals about how much air is coming in.
This can make your car run unevenly, feel sluggish, or even stall, as it can’t quite figure out the right amount of fuel needed. Addressing this involves cleaning the sensor, securing its connections, and making sure it’s giving steady readings so your car can run smoothly again.
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How to fix P0104 – learn from mechanics
I looked into P0104 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Chevrolet P0104
Vehicle Information 1997 Chevrolet Astro 4.3L
Issue + Repair History
- MIL illuminated with code P0104 initially reported, later corrected to P0140 – low O2 activity bank 1 sensor 2.
- TSB 76-65-05 addressed oil-soaked loom, which was resolved.
- Replaced #2 O2 sensor with OE part, but code persisted.
- No exhaust leaks detected; catalytic converter tested with propane, although efficiency was questioned.
- Code takes time to set after driving several miles.
Other OBD2 Codes + Test Results
- No other OBD2 codes reported.
- Exhaust gas readings and manifold vacuum within normal range.
- Fuel pressure normal.
Mechanic Suggestions
- Check wiring and connections for left bank rear sensor (Bank 1 Sensor 2) for issues with heater power, ground, or signal resistance.
- Avoid aftermarket O2 sensors; opt for OEM parts.
- Focus troubleshooting on the O2 sensor rather than the catalytic converter.
- Verify continuity of wiring from sensor to PCM.
- Inspect PCM for water intrusion or fluid contamination.
Final Fix After extensive troubleshooting, the catalytic converter was replaced, and the computer was reset. Following this repair, the P0140 code did not return, indicating successful resolution of the issue.
Case #2: Mercedes P0104
Vehicle Information 2004 Mercedes-Benz S500 4Matic 5.0L
Issue + Repair History
- Check engine light illuminated with codes P0104 and P0103 (airflow meter circuit and high airflow circuit).
- Multiple airflow meters replaced, wiring and harnesses checked and scoped, intake system smoked for leaks.
- Car runs fine for several days, then intermittently surges, runs rough, and triggers P0104 code, particularly after running up to temperature.
Other OBD2 Codes + Test Results
- No additional OBD2 codes detected.
- Live data shows occasional fluctuations in airflow sensor signal.
- Fuel trim levels remain within normal range during operation.
Mechanic Suggestions
- Investigate potential transmission sensor leaks that could affect wiring integrity, leading to fluid ingress into the ECM.
- Check for intermittent opening of the canister purge valve, which could affect engine performance.
- Verify MAF sensor signal using a voltmeter and compare with ECU readings; faulty ECU could misinterpret sensor data.
- Inspect for air leaks at various points in the system, including brakes, EGR, and PCV, particularly under specific drive conditions.
- Monitor voltage on the 5V and 12V wires during operation to ensure they remain within specification, and check ground circuit integrity.
Final Fix Despite extensive troubleshooting, the exact cause of the intermittent issue was not identified. However, after monitoring voltage levels and ensuring system integrity, including replacing the airflow meter multiple times, the issue resolved on its own without a specific repair identified. The vehicle was returned to the owner, and no further instances of the MIL illuminating with P0104 occurred.
Case #3: Ford P0104
Vehicle Information 2011 Ford Fusion S 2.5L
Issue + Repair History
- Intermittent problem reported by owner: occasional unresponsive throttle and stalling upon acceleration from standstill.
- History of code P0104 (MAF sensor circuit intermittent).
- Previous shop replaced MAF sensor with Ford OEM part due to the same code and issue persisting.
- No discernible issues observed during scanning; no Freeze Frame data available.
Other OBD2 Codes + Test Results
- No additional OBD2 codes detected during KOER test.
- Live data readings show no abnormalities.
- Vehicle performs normally during test drives; issue does not replicate.
Mechanic Suggestions
- Inspect wiring near the MAF sensor for potential damage or poor connections; consider using a pigtail assembly from Ford for wiring replacement.
- Attempt to capture Freeze Frame data when the issue occurs to gather more information for diagnosis.
- Apply Stabilant 22a to the MAF connector pins to improve electrical connectivity.
- Smoke test the intake manifold to check for leaks and test the integrity of the MAF circuit using a scope, particularly focusing on the 5V reference.
- Throttle body replacement may resolve the issue; inquire with the dealer about potential extended warranty coverage for faulty throttle bodies.
Final Fix After the owner brought the vehicle back with additional codes P2111 and P0104, the throttle body was replaced, resolving the problem. The issue was attributed to the malfunctioning throttle body, and the vehicle’s performance returned to normal after replacement.
How to diagnose P0104
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Inspect and clean the MAF sensor | Removes any dirt or debris that could interfere with the sensor’s accurate measurement of airflow. |
| Check the air intake system for leaks | Ensures no extra air is entering the engine, which could skew the MAF sensor’s readings. |
| Inspect the MAF sensor’s wiring | Looks for any electrical issues that might cause intermittent signals. |
| Use diagnostic tools | Helps in identifying and analyzing intermittent patterns in the MAF sensor’s signal. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko