Refer to
Engine Data Sensors -- A/C Refrig Press, TP, MAP, ECT, IAT
.
Circuit Description
The powertrain control module (PCM) uses the 5 volt reference B circuit as a sensor feed to the A/C pressure sensor. The PCM monitors the voltage on the 5 volt reference B circuit. If the voltage is out of tolerance, the PCM sets DTC P1639.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The PCM detects a voltage out of tolerance condition on the 5 volt reference B circuit. |
| • | The above condition occurs for more than 30 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/Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has 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 a scan tool. |
Diagnostic Aids
Inspect for the following conditions:
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board (OBD) System Check? | -- | ||
2 |
Is the voltage more than the specified value? | 5.0 V | ||
3 |
Is the voltage more than the specified value? | 0.0 V | ||
4 | Is the voltage less than the specified value? | 4.9 V | ||
5 | Repair a short to voltage in the 5 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |
6 | Repair a short to ground in the 5 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
|
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||
8 | Replace the A/C pressure sensor. Did you complete the replacement? | -- | -- | |
9 |
Does the DTC reset? | -- | System OK |
