Circuit Description
The PCM uses the 5 Volt Reference B circuit as a sensor feed for the A/C Refrigerant Pressure Sensor. The PCM monitors the voltage on the 5 Volt Reference B circuit. If the voltage is out of tolerance, the PCM will set DTC P1639.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | The PCM detects a voltage out of tolerance condition on the 5 Volt Reference B circuit. |
| • | Above condition for longer than 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
Important: : Inspect the PCM and engine grounds for being secure and clean.
Check for the following conditions:
| • | Poor connection at PCM - Inspect harness connectors for the following items: |
| - | Backed out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connections |
| • | Damaged harness - Inspect the wiring harness for damage. |
| • | If the harness appears to be OK, observe the A/C pressure display on the scan tool while moving connectors and wiring harnesses related to the A/C refrigerant pressure sensor. A change in the A/C pressure display will indicate the location of the fault. |
Review the Freeze Frame/Fail Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Visually/physically inspect the PCM and engine grounds. Ensure that the grounds are clean and secure. Did you find and correct the condition? | -- | ||
3 |
Does the scan tool indicate voltage more than the first specified value or less than the second specified value? | 4.8 0.1 V | Go to DTC P0530 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit | |
4 |
Does the voltage measure more than the specified value? | 5.5V | ||
5 |
Does the voltage measure more than the specified value? | 5.5V | ||
6 | Repair short to voltage on the 5 volt reference B circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | -- | |
7 | Does the voltage measure less than the specified value? | 4.5V | ||
8 | Test for a short to voltage in the 5 volt reference B circuit. Refer to Wiring Repairs . Did you find and correct the condition? | -- | ||
9 |
Did you find and correct the condition? | -- | ||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | -- | ||
11 |
Does the DTC reset? | -- | System OK |
