DTC P1538 Air Conditioning (A/C) Request Circuit High Voltage. Oldsmobile Aurora 1997

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1997 🢒 Aurora 🢒 Engine 🢒 Engine Controls - 4.0L and 4.6L 🢒 DTC P1538 Air Conditioning (A/C) Request Circuit High Voltage

DTC P1538 - A/C Request Circuit Voltage High

Engine Controls Components
A/C Compressor Controls
OBD II Symbol Description Notice
ESD Notice
ESD Notice

Circuit Description

This diagnostic test indicates if the A/C request circuit is shorted to voltage. This is done by comparing the A/C Request line (CKT 603) to the serial data received from the HVAC controller. If A/C is not requested by serial data and the A/C Request line (CKT 603 ) is high, voltage present, then DTC P1538 is set.

Conditions for Setting the DTC

Test Conditions

•	DTC P1605 not set.

•	A/C compressor not requested by the HVAC programmer via serial data.

Failure Condition

A/C request line high continuously for 20 seconds.

Action Taken When the DTC Sets

•	Disable the A/C compressor.

•	The Malfunction Indicator Lamp (MIL) will not illuminate.

•	No message will be displayed.

Conditions for Clearing the DTC

•	A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.

•	A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

•	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 in PCM Description and Operation.

Step	Action	Value(s)	Yes	No
1	Was the On-Board Diagnostic (OBD) System Check performed?	--	Go to Step 2	Go to A Powertrain On Board Diagnostic (OBD) System Check
2	Start and idle the engine. Turn the HVAC A/C controls to OFF. Using a scan tool check the DTC information Fail This Ign.. Wait one minute. Has this DTC set?	--	Go to Step 3	Fault not present. Refer to Diagnostic Aids
3	Using a scan tool view the A/C Request display. Does A/C Request display Yes?	--	Go to Step 4	Go to Step 10
4	Disconnect A/C low pressure switch connector. Check the A/C Request display. Does A/C Request display Yes?	--	Go to Step 6	Go to Step 5
5	Reconnect A/C low pressure switch connector. Remove HVAC cont fuse. Check the A/C Request display. Does A/C Request display Yes?	--	Go to Step 7	Go to Step 9
6	Record the fluid life indexes, turn the key to OFF and wait 30 seconds. Disconnect PCM connector C1. Turn the key ON. Using DVM J 39200 measure the voltage to ground at PCM connector C1 terminal 76. Is the voltage more than the value specified?	0.5 volts	Go to Step 8	Go to Step 10
7	Repair the short to voltage on CKT 762. Is the repair complete?	--	Go to Powertrain Control Module Diagnosis for Verify Repair	--
8	Repair the short to voltage on CKT 603. Is the repair complete?	--	Go to Powertrain Control Module Diagnosis for Verify Repair	--
9	Replace the HVAC programmer. Refer to Section 1, Heating and Air Conditioning . Is the replacement complete?	--	Go to Powertrain Control Module Diagnosis for Verify Repair	--
10	Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete?	--	Go to Powertrain Control Module Diagnosis for Verify Repair	--