Rick's Free Auto Repair Advice

Ford P0626

Ford P0626

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.

ford alternator wiring diagram

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

Bad alternator

Wire damage between ALT and PCM

Wire harness chaffing between ALT and PCM

Bad C102A pigtail

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Posted on by Rick Muscoplat

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