The mass air flow sensor (MAF) sits between the air filter and the throttle or compressor and measures how much air the engine draws in; fuel quantity, load and ignition are calculated from it. Most are hot-film or hot-wire sensors that output either a voltage or, on GM, Saab and newer Ford systems, a frequency. P0102 means the signal is below its electrical lower limit – a frequency that is too low or a voltage that is too low. Documented limits: GM petrol 450 Hz or less, GM diesel below 276 Hz, Ford digital below 1.5 kHz for 5 s, Ford analogue below 0.244 V. 'Low' describes the signal: typically an open or grounded signal wire, missing supply voltage or failed electronics. Saab notes that a large leak between sensor and throttle can also cause it. GM and Saab need two trips; the engine runs on a calculated substitute value.
Medium severity. Can I keep driving?You can make a short trip at gentle engine speeds, expecting weak acceleration. If the engine shuts off when you stop or will not rev above low RPM, stay off highways and call for roadside assistance.
Symptoms
- Check engine light on
- Lack of power, hesitation, substitute value mode
- Rough idle or stalling
- Higher fuel consumption
Most likely causes
- Signal wire open or shorted to ground, connector corroded or loose
- Sensor electronics failed
- Missing supply voltage (fuse, relay) or poor ground
- Large leak or disconnected duct between sensor and throttle
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
- It can trigger limp mode.
- It affects emissions.
What each character of P0102 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- 02: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0102?
You can make a short trip at gentle engine speeds, expecting weak acceleration. If the engine shuts off when you stop or will not rev above low RPM, stay off highways and call for roadside assistance.
What causes code P0102?
The most common causes are: signal wire open or shorted to ground, connector corroded or loose; sensor electronics failed; missing supply voltage (fuse, relay) or poor ground.
Related codes
- P0100Mass or Volume Air Flow Sensor A Circuit
- P0101Mass or Volume Air Flow Sensor A Circuit Range/Performance
- P0103Mass or Volume Air Flow Sensor A Circuit High
- P0104Mass or Volume Air Flow Sensor A Circuit Intermittent
- P010CMass or Volume Air Flow Sensor B Circuit Low
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
- newtonnet.co.uk: fordobd2012
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.