P1376

Circuit Description

The PCM applies 2.5 volts on the Ref Lo voltage (CKT 453) circuit to the Ignition Control Module. Ref Lo voltage to the PCM represents the voltage difference between Ref Lo and the PCM power ground. This is needed to ensure that the PCM and IC module signals all have the same ground reference. If the Ref Lo input voltage goes too high or low, DTC P1376 will set.

Conditions for Running the DTC

DTC P0560 is not set.

Conditions for Setting the DTC

^ Ignition Control Module Ref Lo input is +3.98 volts or greater for 1 second.
OR
^ Ignition Control Module Ref Lo input is -1.04 volts or less for 1 second.

Action Taken When the DTC Sets

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.

Conditions for Clearing the DTC

^ The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes. Reading and Clearing Diagnostic Trouble Codes

Diagnostic Aids

This DTC may set due to an improperly installed PCM. This may cause the PCM to not be electrically isolated from the body ground.
Using the scan tool the normal average Ret Lo voltage displayed is 0.00 volts + or -0.20 volts.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. If the snapshot ignition ground voltage is 1.1 volt or less, this means that the PCM ground voltage is floating high causing P1376 to set.
5. Voltage measured at ignition control module connector C4 terminal F should be less than 0.1 volt. If the voltage is higher, then the module must have a bad ground causing the module to try to ground through the Ref Lo input to the PCM.