P0532-A/C Sending Unit Volts Too Low

P0532-A/C SENDING UNIT VOLTS TOO LOW

WHEN MONITORED
With the ignition on and battery voltage greater than 10.4 volts.
SET CONDITION
The circuit voltage to the ECM falls below a calibrated threshold for a certain period of time.
POSSIBLE CAUSES
- Other DTC's
- A/C Pressure sensor
- (C918) signal circuit shorted to (K55) return circuit
- (F855) 5-volt supply circuit shorted to (K55) return circuit
- (C918) Signal circuit open from ECM harness connector to A/C harness connector
- (F855) 5-volt supply circuit open from ECM harness to A/C harness connectors
- (C918) signal circuit shorted to ground
- (F855) 5-volt supply circuit shorted to ground
- ECM
- Intermittent condition
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
DIAGNOSTIC TEST
1. OTHER DTC'S
Turn the ignition on.
With the scan tool, read DTCs.
Q: Are other DTC's present?
YES: Repair other DTC's first. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
NO: Go To 2
2. HARNESS OPEN

Disconnect the A/C pressure sending unit harness connector.
Check connectors - Clean/repair as necessary.
Measure the voltage between the (F855) 5-volt supply and (K916) return circuits of the sensor harness connector.
Q: Is the voltage between 4.5 and 5.5 volts?
YES: Go To 3
NO: Go To 4
3. A/C PRESSURE SENSOR

While monitoring scan tool, use a jumper wire to connect the (F855) 5-volt supply circuit to the (C918) signal circuit at the sensor harness connector.
Q: Did P0533 set?
YES: Replace the A/C pressure sensor. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
NO: Go To 4
4. (C918) SIGNAL CIRCUIT SHORTED TO THE (K916) RETURN CIRCUIT

Turn the ignition off.
Disconnect the ECM harness connectors.
Measure the resistance between the (C918) signal circuit and (K916) return circuit in the sensor harness connector.
Q: Is the resistance greater than 100k Ohms?
YES: Go To 5
NO: Repair the (C918) signal circuit shorted to the (K916) return circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
5. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO THE (K916) RETURN CIRCUIT

Measure the resistance between the (F855) 5-volt supply circuit and (K916) return circuit in the sensor harness connector.
Q: Is the resistance greater than 100k Ohms?
YES: Go To 6
NO: Repair the (F855) 5-volt supply circuit shorted to the (K916) return circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
6. (C918) SIGNAL CIRCUIT OPEN FROM ECM HARNESS CONNECTOR TO A/C

Measure the resistance of the (C918) signal circuit between the sensor harness connector and the ECM harness connector.
Q: Is the resistance less than 10 Ohms?
YES: Go To 7
NO: Repair the open (C918) signal circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
7. (F855) 5-VOLT SUPPLY CIRCUIT OPEN FROM ECM HARNESS CONNECTOR TO A/C HARNESS CONN

Measure the resistance of the (F855) 5-volt supply circuit between the sensor harness connector and the ECM harness connector.
Q: Is the resistance less than 10 Ohms?
YES: Go To 8
NO: Repair the open (F855) 5-volt supply circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
8. (C918) SIGNAL CIRCUIT SHORTED TO GROUND

Measure the resistance between the (C918) signal circuit in the sensor harness connector and battery negative.
Q: Is the resistance greater than 100k Ohms?
YES: Go To 9
NO: Repair the (C918) signal circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
9. (F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND

Measure the resistance between the (F855) 5-volt supply circuit in the sensor harness connector and battery negative.
Q: Is the resistance greater than 100k Ohms?
YES: Go To 10
NO: Repair the (F855) 5-volt supply circuit shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test - Ver 1
10. ECM

Reconnect the ECM harness connectors.
Turn the ignition on.
While monitoring scan tool, use a jumper wire to connect the (F855) 5-volt supply circuit with the (C918) signal circuit at the sensor harness connector.
Q: Did DTC P0533 set?
YES: Test Complete.
NO: Replace the ECM