DTC P1635 5 Volt Reference Circuit. Oldsmobile Intrigue 1998

For 1990-2009 cars only

Makes 🢒 Oldsmobile 🢒 1998 🢒 Intrigue 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P1635 5 Volt Reference Circuit

Engine Controls Components
Engine Data Sensors-MAF, EVAP Vent, EVAP Purge, EGR
OBD II Symbol Description Notice

Circuit Description

The PCM uses the 5 Volt Reference A circuit as a sensor feed to the following sensors:

•	The TP sensor.

•	The MAP sensor.

•	The EGR Valve Pintle Position sensor.

The PCM monitors the voltage on the 5 Volt Reference A circuit. If the voltage is out of tolerance, the PCM will set DTC P1635.

Conditions for Setting the DTC

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

•	The above condition is present for longer than 10 seconds.

Action Taken When the DTC Sets

•	The PCM will illuminate the 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 Fail Records data.

Conditions for Clearing the MIL/DTC

•	The PCM will turn the MIL OFF 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 Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids

Important:: Be sure to inspect PCM and engine grounds for being secure and clean.

Check for the following conditions:

•	Poor connection at the PCM.

Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

•	Damaged harness.

Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool with the ignition ON, engine not running while moving connectors and wiring harnesses related to the following sensors. A change in the MAP display will indicate the location of the malfunction.

-	The TP sensor.

-	The MAP sensor.

-	The EGR valve.

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

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

This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

DTC P1635 - 5 Volt Reference A Circuit

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

Important: Visuallyphysically check the PCM and engine grounds. Ensure that the grounds are clean and secure. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Using the scan tool, check for any of the following DTCs:

•	DTC P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage

•	DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage

•	DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

•	DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage

•	DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit

•	DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance

•	DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage

•	DTC P1106 Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent High Voltage

•	DTC P1107 Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage

•	DTC P1121 Throttle Position (TP) Sensor Circuit Intermittent High Voltage

•	DTC P1122 Throttle Position (TP) Sensor Circuit Intermittent Low Voltage

•	DTC P1404 Exhaust Gas Recirculation (EGR) Closed Position Performance

Are any of the DTCs set?

Diagnose the applicable DTC

Go to Step 3

Turn the ignition switch to the OFF position.
Disconnect the MAP sensor, TP sensor, and the EGR connectors.
Connect J 39200 digital multimeter (DMM) between the 5V reference and sensor ground in the TP sensor connector.
Turn the ignition switch to the ON position.

Does the DMM display a voltage near the specified value?

Go to Step 4

Go to Step 6

Leave the DMM connected to the TP sensor.
Leave the ignition switch turned to the ON position.
Reconnect the MAP sensor.
If the voltage changes when the MAP sensor is reconnected, replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .

Was a problem found?

Go to Step 16

Go to Step 5

Turn the ignition switch to the OFF position.
Connect the DMM to the 5V reference and sensor ground in the EGR connector.
Turn the ignition switch to the ON position.
Reconnect the TP sensor.

Does the DMM display a voltage near the specified value?

Go to Step 9

Go to Step 12

Does the DMM display a voltage greater than the specified value?

Go to Step 7

Go to Step 8

Leave the DMM connected to the 5V reference and sensor ground in the TP sensor connector.
Turn the ignition switch to the OFF position.
Disconnect the PCM.
Turn the ignition switch to the ON position.

Does the DMM display a voltage greter thant the specified value?

Go to Step 14

Go to Step 15

Leave the sensors disconnected.
Turn the ignition switch to the OFF position.
Disconnect the PCM.
Check for a short between the 5V reference and the following circuit(s):

•	sensor or engine ground.

•	EGR control circuit.

If a problem is found, repair as necessary. Refer to Repair Procedures in Wiring Repairs .

Was a problem found?

Go to Step 16

Go to Step 15

Connect the DMM between the EGR control and EGR sensor ground circuits in the EGR connector.

Does the DMM display a voltage near the specified value?

B+

Go to Step 13

Go to Step 10

Leave the DMM connected.
Turn the ignition switch to the OFF position.
Disconnect the PCM.
Turn the ignition switch to the ON position.

Does the DMM display a voltage near the specified value?

Go to Step 15

Go to Step 11

Locate and repair the short between the 5V reference and the EGR control circuit. Refer to Repair Procedures in Wiring Repairs .

Is action complete?

Go to Step 16

Replace the TP sensor. Refer to Throttle Position Sensor Replacement .

Is action complete?

Go to Step 16

Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement

Is action complete?

Go to Step 16

Locate and repair the short to voltage in the 5V reference circuit. Refer to Repair Procedures in Wiring Repairs .

Is action complete?

Go to Step 16

Replace the PCM.

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

Is action complete?

Go to Step 16

Review and record scan tool Fail Records data.
Clear the DTCs.
Operate the vehicle within the Fail Records conditions.
Using the scan tool, monitor Specific DTC info for DTC P1635.

Does the scan tool indicate that DTC P1635 failed this ign?

Go to Step 2

System OK