P0102: Mass or Volume Air Flow "A" Circuit Low

What does P0102 mean?

The MAF sensor reports the amount of air entering the engine so the ECM can set fuel delivery and ignition timing. P0102 sets when the signal voltage or frequency stays below the expected range.

A low circuit code points more strongly to an electrical cause than P0101 does. An unplugged connector, a damaged wire or a failed sensor are typical reasons.

Common symptoms

• Check engine light on
• Often no other noticeable symptoms
• Possible poor fuel economy or rough running

Common causes

The causes below are the ones commonly seen with P0102. The actual cause can vary by vehicle, engine and mileage, so treat this list as a starting point, not a diagnosis.

• The MAF sensor is unplugged or its wiring is damaged
• Loose or corroded terminals in the MAF circuit
• A failed MAF sensor

What to check with a scanner

• Check that the MAF connector is fully seated and the terminals are clean.
• Look for chafed wiring along the intake duct.
• In Live data, check the MAF reading with the engine idling. A value near zero points to a circuit problem.
• Clear the code after a repair and confirm it does not return on a test drive.

How to read and clear P0102 with OBD Master Pro

1. Plug in your adapter. Connect a generic ELM327 (or ELM329) OBD2 adapter to the diagnostic port, usually under the dashboard on the driver's side. Bluetooth Classic, Bluetooth LE, Wi-Fi and USB OTG adapters are supported.
2. Switch the ignition on. Turn the key to ON or start the engine, depending on your car.
3. Connect in OBD Master Pro. Open the app, go to Connection and pick your adapter. Classic Bluetooth adapters connect from the Bluetooth tab, Bluetooth LE adapters from the BLE tab with no pairing needed. Use the generic OBD2 / EOBD profile or your car's brand profile.
4. Read the codes. Open the fault codes screen to see stored, pending and permanent codes. Confirm P0102 is listed and note any other codes, since they often explain the cause.
5. Check the details. Look at freeze frame data, Live data and, where your car supports it, Mode 06 test results (see the checks above).
6. Fix, then clear. After the repair, clear the codes to turn off the check engine light. Clearing also resets the emissions readiness monitors, so drive normally and check the readiness screen before any inspection. Permanent codes cannot be erased with a scan tool; they clear on their own once the car's self test passes.

Tip: you can also look up P0102 and other codes in the app's DTC search without connecting to a car. If your adapter will not connect, use Connection > Share connection log and email it to support. Many cheap ELM327 clones only handle basic engine OBD2, which is all you need for P0102.

When to see a mechanic

Get professional help if any of these apply:

• The connector and wiring look fine but the code returns
• You need voltage and ground tests at the sensor
• The engine stalls or runs poorly

If you are unsure, a qualified technician can confirm the cause with tests such as smoke testing, pressure testing or scope readings. Clearing a code does not repair the fault.

Related trouble codes

See all OBD2 trouble code guides

Related guides

Check engine light on: what to do · How to read an OBD2 code (P, B, C, U) · Stored, pending and permanent codes and freeze frame · OBD2 readiness monitors explained · OBD2 glossary · OBD2 by car brand