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DTC P0622: Generator Field Not Switching Properly

NOTE: Diagnostic Trouble Code (DTC P0622) is set when Powertrain Control Module (PCM) attempts to regulate generator field with no result during monitoring.

Possible Causes:

Testing

  1. Turn ignition on, engine not running. Record all DTC's and the related Freeze Frame data. Check for any related TSB's. Using a 12-volt test light connected to ground, backprobe the (K20) generator field control circuit at the back of the generator. With the DRBIII(R), actuate the Generator Field Driver. If the test light blinks, go to INTERMITTENT CONDITION  under SYSTEM TESTS and VER-3 TEST  . If the light does not blink, go to next step.
  2. Backprobe the (K125) generator field source circuit at back of generator with a volt meter. With the DRBIII(R), actuate the generator field driver. If the voltage is above 10 volts, go to next step. If the voltage is not above 10 volts, repair the open in the (K125) generator field source circuit. Perform Verification Test Ver-3. See VER-3 TEST  under VERIFICATION TESTS.
  3. Turn the ignition off. Disconnect the PCM harness connectors. Disconnect the Generator Field harness connector. Measure the resistance of the (K20) generator field control circuit from the Generator Field harness connector to the PCM harness connector. If the resistance is below 5 ohms, go to next step. If the resistance is above 5 ohms, repair the open in the (K20) generator field control circuit. Perform Verification Test Ver-3. See VER-3 TEST  under VERIFICATION TESTS.
  4. Measure the resistance between ground and the (K20) generator field control circuit in the PCM harness connector. If the resistance is below 100 ohms, repair the short to ground in the (K20) generator field control circuit. Perform Verification Test Ver-3. See VER-3 TEST  under VERIFICATION TESTS. If the resistance is above 100 ohms, go to next step.
  5. Measure resistance across the Generator Field Terminals at the generator. If the resistance is between 0.5 of an ohm and 15 ohms, go to the next step. If the resistance is not as specified, repair the generator as necessary. Perform Verification Test Ver-3. See VER-3 TEST  under VERIFICATION TESTS.
    6. NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
  6. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits. If there are no possible causes remaining, replace and program the Powertrain Control Module. Perform Verification Test Ver-3. See VER-3 TEST  under VERIFICATION TESTS.
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