Circuit Description
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 J 39200 .
Conditions for Running the DTC
| • | 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). |
Conditions for Setting the DTC
The PCM senses system voltage below 8 volts for 5 seconds.
Action Taken When the DTC Sets
| • | 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. |
Conditions for Clearing the DTC
| • | 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. |
Diagnostic Aids
Important:
• Remove any debris from the PCM\TAC module connector surfaces before
servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets
when diagnosing/replacing the modules. Ensure that the gaskets are installed
correctly. The gaskets prevent contaminate intrusion into the PCM\TAC
modules. • 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.
| • | The following may cause an intermittent: |
| - | Poor connections; Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. |
| - | Mis-routed harness. |
| - | Rubbed through wire insulation. |
| - | Broken wire inside the insulation. |
| • | 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. |
| • | Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed. |
| • | For an intermittent, refer to Symptoms . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the Charging system under a load at idle. The voltage should remain above 8.0 volts.
Step | Action | Value(s) | 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 using the scan tool. Does the scan tool display the specified value? | B+ | Go to Charging System Check 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 using the DMM J 39200 . 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. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement . Replace the PCM. 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 using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
