The PCM continuously monitors the system voltage. The system voltage information is taken from the PCM's ignition feed circuit. When the PCM detects a high or low voltage condition, the PCM operates in a default mode. If the system voltage is low, the PCM raises the idle speed in order to increase the generator output. If the system voltage is high, the PCM disables most outputs in order to protect the hardware . The Class 2 Serial Data circuit is shut down when system voltage is below 9.2 volts or above 16 volts. A scan tool may not display data if system voltage is outside of this range. Because of this, monitor the system voltage when diagnosing a current condition using a DMM .
• | The engine operates longer than 10 seconds. |
• | The engine speed is greater than 1000 RPM. |
• | The vehicle speed is greater than 8 km/h (5 mph). |
The PCM senses system voltage below 8 volts for 5 seconds.
• | The PCM stores DTC P0562 in memory when the diagnostic runs and fails. |
• | The malfunction indicator lamp (MIL) will not illuminate. |
• | The PCM will record the operating conditions at the time during which the diagnostic fails. The PCM stores this information in the Failure Records. |
• | High idle speed |
• | The transmission defaults to third gear. |
• | The TCC operation is inhibited. |
• | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
• | A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
• | Use a scan tool in order to clear the DTC. |
Important:
• Remove any debris from the PCM connector surfaces before servicing
the PCM. Inspect the PCM connector gaskets when diagnosing/replacing
the module. Ensure that the gaskets are installed correctly. The
gaskets prevent contaminate intrusion into the PCMs. • For any test that requires probing the PCM or a component
harness connector, use the Connector Test Adapter Kit J 35616
. Using this kit prevents damage
to the harness/component terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
• | An extremely low voltage (below 7.5 volts) may cause the loss of serial data and the MIL may not function. An open ignition feed circuit causes a no start and the MIL will not illuminate. A low system voltage may cause other DTCs to set. |
• | For an intermittent, refer to Symptoms . |
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Important: If DTC P1637 is also set, refer to DTC P1637 Generator L-Terminal Circuit or DTC P1638 Generator F-Terminal Circuit for further diagnosis. Ensure the battery is fully charged before proceeding with this diagnostic. Monitor the Ignition 1 Voltage with the scan tool. Does the scan tool display the specified value? | B+ | Go to Diagnostic System Check - Engine Electrical in Engine Electrical | ||
3 | Inspect the PCM fuse for being open. Is the fuse open? | -- | ||
4 |
Is the voltage at the specified value? | B+ | ||
5 | Test the continuity of the ignition feed circuit with the DMM . Refer to Testing for Continuity in Wiring Systems. Does the DMM display continuity below the specified value? | 5ohms | ||
6 | Repair the ignition feed circuit to the PCM for an open or a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
7 |
Did you find and correct the condition? | -- | ||
8 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
9 |
Does the scan tool indicate that this test ran and passed? | -- | ||
10 | Select the Capture Info option and the Review Info option with the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |