Home » GM 6.5 » GM/Detroit 6.5L ENGINE CONTROLS – DTC P1635 5 Volt Reference Low

GM/Detroit 6.5L ENGINE CONTROLS – DTC P1635 5 Volt Reference Low

Circuit Description
The PCM provides a 5 vol t supply for use in powering up sensors. This test monitors the voltage present at terminals BRD13 (shared by Boost, EGR control pressure/BARO and crankshaft position sensors) and BRD14 (optical/fuel temperature sensor (cam/hl.res).

Conditions for Running the DTC
The ignition switch in the ON position.

Conditions for Setting the DTC
5 volt reference is less than 1 volt.

Action Taken When the DTC Sets
• The PCM will not il luminate the malfunction indicator lamp (MIL).
• The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Failure Records.

Conditions for Clearing the MIL/DTC
• A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures
• The use of a scan tool.

Diagnostic Aids
During the time the failure is present, the setting of additional DTCs that share a 5 volt reference may also set.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. Checks to confirm that a DTC is still present.

3. Checks to determine if there is a 5 volt reference from the PCM.
4. Checks to determine if there is a short-to-ground in the reference circuit or a short-to-ground in the PCM.
7. This step determines if the short is being caused by one of the sensors on the engine or the short is in the wiring harness.


Leave a Reply

Your email address will not be published. Required fields are marked *