MAF Codes 26/56/66 Troubleshooting
Codes Definitions: 26 - Mass Air Flow Sensor was greater than 0.7 volts with engine off (O), MAF sensor was not between 0.2 and 1.5 volts with engine running (R).
56 - Mass Air Flow/Vane Air Flow Sensor Circuit Above Maximum Voltage (O,CM,R)
66 - MAF input voltage went below minimum test voltage of .40vdc during engine operation (CM,R) or during KOEO (O).
Mass Air Flow (MAF) SensorTools Required: (in addition to the generic tools)- Digital VOM or DMM
- Wiring diagrams for your year Mustang
- Vacuum diagram for your year Mustang
Testing Procedure:1. For codes 26 and 66 perform the tests indicated in the following diagram.
2. If OK, check wire integrity to the ECM connector pins using the correct wiring diagram you'll find in this section of my5oh.com. Resistance reading should be less/equal to 5 ohms...NOK?...trace and correct open wire condition.
3. If results are OK, you might have an intermittent MAF sensor, connection, radiator fan wash turbulence affecting MAF readings, a boost bypass valve creating air flow ripple or an intermittent ECM.
4.
For code 56, clear codes, disconnect MAF sensor, start and idle engine for 1-minute, rerun KOEO self-test and check for code 56 to show up....it doesn't?...replace MAF....it does?....goto 5.
5. Disconnect MAF sensor and ECM, Ign Off, measure resistance between MAF SIG and VPWR pins at the MAF harness connector...resistance over 10,000 ohms?......YES?....Bad ECM.....NO?...MAF SIG and VPWR wires are shorted, trace and repair.
Hope this helps someone....