DTC P1639 5 Volt Reference 2 Circuit. Oldsmobile Intrigue 1999

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1999 🢒 Intrigue 🢒 DTC 🢒 DTC P1639 5 Volt Reference 2 Circuit

Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice

Circuit Description

The powertrain control module (PCM) uses the 5 volt Reference B circuit as a sensor feed for the following sensors:

•	The A/C refrigerant pressure sensor.

•	The fuel tank 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 Setting the DTC

•	The PCM detects a voltage out of tolerance condition on the 5 volt Reference B circuit.

•	Above condition is present for longer than 10 seconds.

Action Taken When the DTC Sets

The PCM stores the conditions which were present when the DTC set as Fail Records data only.

Conditions for Clearing the MIL/DTC

•	A history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.

•	The DTC may be cleared using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids

Important: Verify that the PCM and engine grounds are secure and clean.

Inspect for the following conditions:

•	A faulty connection at the PCM. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections.

•	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 the connectors and wiring harnesses related to the A/C refrigerant pressure sensor. A change in the A/C pressure display indicates the location of the malfunction.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

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

This vehicle is equipped with a powertrain control module (PCM) which utilizes an electrically erasable programmable read-only memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

DTC P1639 - 5 Volt Reference B Circuit

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Visually/physically inspect the PCM and engine grounds. Ensure that the grounds are clean and secure.
If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

Go to Step 12

Go to Step 3

Turn off the ignition switch.
Disconnect the fuel tank pressure (FTP) sensor connector.
Connect a digital multimeter (DMM) between the 5 V reference and sensor ground in the FTP sensor connector.

Is the voltage more than the specified value?

5 V

Go to Step 4

Go to Step 5

Leave the DMM connected.
Turn off the ignition switch.
Disconnect the PCM connector.
Turn on the ignition switch.

Is the voltage more than the specified value?

5 V

Go to Step 8

Go to Step 11

Is the voltage less than the specified value?

5 V

Go to Step 6

Go to Step 9

Leave the DMM connected to the 5 V reference and sensor ground circuits in the FTP connector.
Disconnect the A/C pressure sensor connector.

Is the voltage near the specified value?

5 V

Go to Step 10

Go to Step 7

Turn off the ignition switch.
Leave the FTP and the A/C pressure sensors disconnected.
Disconnect the PCM connector.
Test the 5 V reference for a short to chassis or sensor ground.
If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

Go to Step 12

Go to Step 11

Locate and repair the short to voltage in the following circuits:

•	The 5 V reference circuit.

•	The FTP sensor signal circuit

•	The A/C pressure sensor signal circuit

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 12

Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement .

Did you complete the repair?

Go to Step 12

Replace the A/C Pressure Sensor. Refer to A/C Refrigerant Pressure Sensor Replacement in HVAC System - Manual.

Did you complete the repair?

Go to Step 12

Important: The replacement PCM must be reprogrammed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Did you complete the repair?

Go to Step 12

Review and record the scan tool Fail Records data.
Clear the DTCs.
Operate the vehicle within the Fail Records conditions.
Use the scan tool in order to monitor the Specific DTC info for DTC P1639.

Does the scan tool indicate that DTC P1639 Failed This Ign?

Go to Step 3

System OK