P1537

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

This diagnostic indicates very low refrigerant pressure or an open low pressure switch/circuit by comparing the A/C request discrete line, which contains the low pressure switch, to the HVAC serial data A/C request status. If the A/C request line is low, no voltage present, while the HVAC serial data is requesting A/C operation then DTC P1537 is set.

CONDITIONS FOR RUNNING THE DTC

^ DTC P1605 not set.

^ A/C compressor requested by the HVAC programmer serial data.

CONDITIONS FOR SETTING THE DTC

A/C request line low, no voltage present, for 30 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ Disable 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.

^ PCM battery voltage is interrupted.

^ Using a Scan tool.

DIAGNOSTIC AIDS

If fault is not present operate the vehicle with a manifold gauge connected and watch for low A/C system pressure with engine and A/C ON for an extended period.

Whenever A/C request line is checked for voltage the engine must be running.

TEST DESCRIPTION

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

2. Checking if fault is present.

3. Checking if fault is circuit or sensor I pressure problem. Disabling the A/C compressor is required for system protection.

4. Checking for voltage to switch.

5. Checking for the A/C Low Pressure Switch (A/C Request) circuit shorted to ground.

6. Checking for an open in the A/C Low Pressure Switch (A/C Request) circuit.

7. Checking for voltage output from HVAC.