Circuit Description
The following DTCs are for internal failures within the hybrid control module (HCM):
| • | P1AC8 is HCM 5-volt reference circuit. |
| • | P0A1D is HCM internal system fault. |
HCM System Fault Diagnostic - P0A1D
There are 3 parts to the HCM system fault diagnostic. Any of the 3 may cause the diagnostic to be reported as failed. Only if all 3 are passed may the diagnostic be reported as passed. The first reports software execution errors with in the HCM software scheduler, system and user stacks, interrupt and input/output subsystems. Once detected, this fault will report an HCM system diagnostic fault for the rest of the current ignition cycle. The second detects a stuck on situation where all of the inputs indicate that the HCM should be OFF, but the main code is still executing. This could occur, for example, due to an HCM internal hardware fault. Once detected, this fault will report an HCM system diagnostic fault for the rest of the current ignition cycle. The final input is based upon the HCM system voltage. If the supply voltage to the HCM, as measured at the ignition 0 analogue input is out of range a fault flag is raised.
5-Volt Regulator Diagnostic - P1AC8
The HCM 5-volt regulator diagnostic employs three tests. The first test diagnoses the 5-volt regulator from the internal HCM hardware line. This line is switched high when the 5-volt regulator hardware detects one of the following faults: gross out of regulation, low input voltage, high input voltage, shorted load, over temperature. In the event that the 5-volt line goes high, a fail flag will be raised. The second test compares the 5-volt external reference analogue measurement with an expected range. If the analogue reading is outside of the valid range, either the 5-volt external or the supply/reference is out of regulation and a fail flag is raised. An additional test detects if the external 5-volt regulator is stuck ON. At power up, before the regulator is enabled, the regulator voltage is observed through its analogue input channel. If this reading indicates that 5 volts is present, the 5-volt regulator diagnostic is reported failed for the remainder of the trip.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0A1D HCM System Fault
Conditions for Running the DTC
| • | Engine running for 30 seconds |
| • | The HCM has received voltage on the ignition 0 voltage circuit. |
| • | The HCM has turned ON and no configuration DTC are present. |
| • | This diagnostic will be run every 100 ms. |
| • | Reference voltage is stable and accurate. |
Conditions for Setting the DTC
| • | P1AC8 is HCM 5-volt reference circuit. |
| • | P0A1D is HCM internal system fault. |
Action Taken When the DTC Sets
| • | The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Hybrid Controls Schematics Connector End View Reference: Hybrid Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Is the DTC set as current DTC? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections |
3 | Inspect for poor connections at the harness connector of the HCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 5 | Go to Step 4 |
4 | Replace the HCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 5 | -- |
5 |
Does the DTC reset? | Go to Step 2 | System OK |
