Diagnose and fix Ford P0626
A Ford P0626 is defined as Generator Field Terminal Circuit High. This means the GENMON circuit is either open or shorted to power. In normal operation, the PCM monitors the alternator output via the GENMON terminal connected to the alternator and PCM. This is a frequency signal indicating the amount of charging by the alternator. If the PCM can’t read this frequency signal on the GENMON circuit due to an open in the wire or short-to-ground, the alternator will default to 13.5 volts at 2,000 RPM and send a digital request to the instrument cluster to turn on the charging system warning light.
Diagnose Ford P0626
Step 1: Ford P0626 Diagnose battery condition
Check battery condition. Is voltage above 12.6 volts?
Does battery pass resistance and simulated load test?
Step 2: Ford P0626 Backprobe Terminal 3 at the alternator
With the IGN OFF, check the black/orange/green connection in the alternator C102B connector. It should be battery voltage. Disconnect the connector and check for battery voltage again. If not, check fusible links and splice S120.
Step 3: Ford P0626 Check resistance
Disconnect connector C102A at alternator. Using ohmmeter, check resistance between each terminal and ground.
Terminal 1 should be greater than 1M/1,00K Ω
Terminal 2 should be greater than 125K Ω
Terminal 3 should be greater than 125K Ω
If you don’t get those readings, check for open or excessive resistance.
Step 4: Check GENMON and GENCOM wire continuity between C102A connector and PCM
Most common fixes for Ford P0626
Blown fusible links
Failure at splice S120
Wire damage between ALT and PCM
Wire harness chaffing between ALT and PCM
Bad C102A pigtail
©, 2020 Rick Muscoplat
Posted on by Rick Muscoplat