P0626 - Generator Field/F Terminal Circuit High
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Generator Field/F Terminal Circuit High (P0626). The signal is above the upper threshold, typically from an open circuit, poor connection, or a short to battery voltage.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Generator Field/F Terminal Circuit High – Coil Resistance | Resistance (Ω) | 3 - 30 Ω (typical) | Connector disconnected at 20°C |
| Generator Field/F Terminal Circuit High – Duty Cycle | PWM (%) | 5 - 95 % (modulates with target) | Engine running, actuator in control |
| Generator Field/F Terminal Circuit High – Supply Voltage | Voltage (V) | 11.8 - 14.4 V | Ignition ON at connector |
Connector disconnected at 20°C
Engine running, actuator in control
Ignition ON at connector
Oscilloscope Waveform Analysis
2 ms/div, 20 V/divPossible Causes
Open circuit on signal wire, spread terminal pin, or short to power feed at Generator Field/F Terminal Circuit High
Chafed or pinched wiring harness along the signal path to Generator Field/F Terminal Circuit High
Internal mechanical wear or carbon deposits inside Generator Field/F Terminal Circuit High
Defective internal output driver or reference circuit in the control module for Generator Field/F Terminal Circuit High
Symptoms
4
Recommended Solution
Measure signal terminal voltage with ignition ON and sensor unplugged to determine if ECM pull-up is active or harness is shorted to 12V.
Verify loaded supply voltage and harness terminal pins at Generator Field/F Terminal Circuit High.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Generator Field/F Terminal Circuit High.
Check supply and the low-side driver at the ECM connector. Replace the actuator or repair the circuit based on the readings.
Mechanic's Tip
Use the scan-tool output test with the scope on the control side at the same time. If duty changes but the actuator does not move, the valve is stuck — not the electrical fault you were chasing.