DTC P1540 Air Conditioning (A/C) Refrigerant Overpressure - Air Conditioning (A/C) Disabled. Oldsmobile Aurora 1997

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1997 🢒 Aurora 🢒 DTC 🢒 DTC P1540 Air Conditioning (A/C) Refrigerant Overpressure - Air Conditioning (A/C) Disabled

DTC P1540 - A/C System - High Pressure

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

Circuit Description

This diagnostic detects an over pressure condition in the A/C system. The DTC is set if the A/C high pressure switch, opens at 430 psi, disables the A/C clutch at least 10 times with high side temperature below a threshold. This is designed to detect blockages in the A/C system. When the DTC is set, the A/C clutch will be disabled for the ignition cycle.

Conditions for Setting the DTC

Test Condition

A/C is ON.

Failure Condition

A/C clutch disabled 10 times by the A/C high pressure switch with the A/C high side temperature less than 87°C (109°F).

Action Taken When the DTC Sets

•	Disengage the A/C compressor for the ignition cycle.

•	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.

Diagnostic Aids

Use the Failure Rec. on the scan tool and note the conditions under which the DTC set. If A/C High Side Temp. was close to 87°C (189°F) then a high pressure condition probably occurred, if A/C High Side Temp. was low than an intermittent open circuit or switch probably set this DTC.

Test Description

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

Checking if fault is present.

Checking if fault is pressure or switch / circuit problem.

Step	Action	Value(s)	Yes	No
1	Was the Powertrain On-Board Diagnostic (OBD) System Check performed?	--	Go to Step 2	Go to A Powertrain On Board Diagnostic (OBD) System Check
2	Turn the engine ON and the A/C ON. Using a scan tool check the A/C Hi Press. Sw. display. Does the display indicate Normal?	--	Fault not present. Refer to Diagnostic Aids	Go to Step 3
3	Connect a manifold gauge set to A/C system. Turn the engine ON and the A/C ON. Monitor A/C high side pressure and A/C Hi Press. Sw. display. When the scan tool display indicates Hi Press. is the A/C high side pressure above the value specified?	430 psi	Go to Step 7	Go to Step 4
4	Turn the key to OFF. Disconnect the A/C high pressure switch and PCM connector C1. Check terminal contact at both the A/C high pressure switch and the PCM. Repair terminal contact if needed. Was terminal contact repaired?	--	Go to Powertrain Control Module Diagnosis for Verify Repair	Go to Step 5
5	Check CKT 451, CKT 604 and the ground for CKT 451 for an intermittent open condition. Repair if needed. Was a repair made?	--	Go to Powertrain Control Module Diagnosis for Verify Repair	Go to Step 6
6	Replace the A/C high pressure switch. Refer to Section 1, Heating and Air Conditioning . Is the repair complete	--	Go to Powertrain Control Module Diagnosis for Verify Repair	--
7	Repair the cause of high A/C system pressure. Refer to Section 1, Heating and Air Conditioning . Is the repair complete?	--	Go to Powertrain Control Module Diagnosis for Verify Repair	--