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DTC P0622: Generator Field Not Switching Properly

Possible Causes:

NOTE: Diagnostic Trouble Code (DTC) is set when Powertrain Control Module (PCM) attempts to regulate generator field with no result during monitoring. Possible causes are generator field resistance more than 5 ohms, open generator field driver circuit, generator field driver circuit shorted to ground, defective generator or PCM.

Testing

  1. Turn ignition on. Using scan tool, actuate generator field driver circuit. Using a test light connected to ground, backprobe generator field driver circuit at the back of generator. If test light blinks, go to next step. If test light does not blink, go to step  3 .
    2. NOTE: The conditions that set this DTC are not present at this time. The following tests may help in identifying the intermittent condition.
  2. Turn ignition on. Review the DRBIII(R) freeze frame information. If possible, try to duplicate the conditions under which the DTC was set. With the DRBIII(R), actuate the generator field driver circuit. Wiggle the wire harness from the generator to PCM. If the DTC returns, repair as necessary. Perform VER-3 TEST  under VERIFICATION TESTS. If the DTC does not return, the test is complete.
  3. Turn ignition on. Record all DTCs and freeze frame data. Carefully inspect all connectors for corrosion or spread terminals before continuing. With the DRBIII(R), actuate the generator field driver circuit. Backprobe the generator field source (+) circuit at back of generator with a voltmeter. If the voltage is above 10 volts, go to next step. If the voltage is less than 10 volts, repair the open in the generator field source (+) circuit. Perform VER-3 TEST  under VERIFICATION TESTS.
  4. Turn the ignition off. Disconnect the PCM harness connectors. Disconnect the generator field harness connector. Measure the resistance between ground and the generator field driver circuit in the PCM harness connector. If the resistance is below 100 ohms, repair the short to ground in the generator field driver circuit. Perform VER-3 TEST  under VERIFICATION TESTS. If the resistance is above 100 ohms, go to next step.
  5. With the ignition off, disconnect the PCM harness connectors. Disconnect the generator field harness connector. Check connectors, clean and repair as necessary. Measure the resistance of the generator field driver circuit between the PCM harness connector and the generator field 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 generator field driver circuit. Perform VER-3 TEST  under VERIFICATION TESTS.
  6. With the ignition off, disconnect the generator field harness connector. Measure the resistance across the generator field terminals at the generator. If the resistance is below 0.5 ohms, replace the generator. See GENERATOR  under REMOVAL & INSTALLATION. Perform VER-3 TEST  under VERIFICATION TESTS. If the resistance is below 0.5 ohms, go to next step.
  7. With the ignition off, disconnect the generator field harness at the back of the generator. Check connectors, clean and repair as necessary. Measure resistance across the generator field terminals at the generator. If the resistance is above 15 ohms, replace the generator. See GENERATOR  under REMOVAL & INSTALLATION. Perform VER-3 TEST  under VERIFICATION TESTS. If the resistance is below 15 ohms, go to next step.
  8. If there are no possible causes remaining, replace and program the Powertrain Control Module. See REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE article. Perform VER-3 TEST  under VERIFICATION TESTS.
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