DTC P1635 5 Volt Reference Circuit. Buick GL7 (Export) 2000

For 1990-2009 cars

### 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 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 A circuit.

• | Above condition for more 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/Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC clears after 40 malfunction free warm-up cycles.

• | The PCM receives a clear code command from the scan tool.

### Diagnostic Aids

Inspect for the following conditions:

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.

• | Poor terminal connection-Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension.

• | 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.

• | PCM and engine grounds for clean and secure connections

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

### Test Description

The numbers below refer to the step numbers on the diagnostic table:

1. The 5 volt reference circuit for these components is shared within the PCM. A short at any component could affect the entire 5 volt reference circuit.

2. The 5 volt reference circuit for these components is shared within the PCM. A short at any component could affect the entire 5 volt reference circuit. The fuel level signal circuit although not included in the 5 volt reference circuits, if shorted to ground will affect other 5 volt reference circuits.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Start and idle the engine for 2 minutes or until this DTC sets. Did this DTC fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids

3

1. Turn the ignition OFF.
2. Disconnect the TP sensor.
3. Turn the ignition ON while leaving the engine OFF.
4. Using a DMM, measure the voltage between the 5 volt reference circuit and ground.

Is the voltage between the specified range?

4.8 -5.2V

Go to Step 9

Go to Step 4

4 | Is the voltage more than the value specified? | 5.2V | Go to Step 5 | Go to Step 7

5

1. Continuously monitor and record the 5 volt reference circuit voltage at the TP sensor as you disconnect the following components:

• | EGR valve

• | MAP sensor

• | Fuel level sensor

2. Using a DMM measure the voltage between the 5 volt reference circuit and ground at the TP sensor connector.

Is the voltage more than the value specified?

5.2V

Go to Step 6

Go to step 11

6

1. Turn the ignition OFF.
2. Disconnect the PCM.
3. Turn the ignition ON.
4. Using a DMM, measure the VOLTAGE between ground and the 5 volt reference circuit for each of the following components:

• | TP sensor

• | EGR valve

• | MAP sensor

• | Fuel level sensor

Is the voltage ever more than the value specified?

0.0V

Go to Step 12

Go to Step 16

7

1. Continuously monitor the 5 volt reference circuit voltage at the TP sensor as you disconnect the following components:

• | EGR valve

• | MAP sensor

• | Fuel level sensor

2. Using a DMM, measure the voltage between the 5 volt reference circuit and ground at the TP sensor connector.

Is the voltage within the specified range value?

4.8-5.2V

Go to Step 13

Go to Step 8

8

1. Turn the ignition OFF.
2. Disconnect the PCM.
3. Turn the ignition ON.
4. Using a DMM, measure the RESISTANCE between ground and the 5 volt reference circuit for each of the following components:

• | TP sensor

• | EGR valve

• | MAP sensor

• | Fuel level sensor

Is continuity every indicated?

--

Go to Step 14

Go to Step 16

9 | Observe the TP angle display on the scan tool with the TP sensor disconnected. Is the TP angle more than the value specified? | 0% | Go to Step 15 | Go to Step 10
10 | Replace the shorted to ground TP sensor. Is the replacement complete? | -- | Go to Step 17 | --
11 | The component, that when disconnected caused the 5 volt reference circuit to return to normal has a short to voltage on the SIGNAL circuit. Repair the circuit as necessary. Is the repair complete? | -- | Go to Step 17 | --
12 | Repair the short to voltage on the affected 5 volt reference circuit. Is the repair complete? | -- | Go to Step 17 | --
13 | Replace the component that when disconnected caused the 5 volt reference voltage to return to normal. Is the replacement complete? | -- | Go to Step 17 | --
14 | Repair the short to ground on the affected 5 volt reference circuit. Is the repair complete? | -- | Go to Step 17 | --
15 | Repair the TP signal circuit shorted to battery voltage condition. Is the repair complete? | -- | Go to Step 17 | --
16 | Important: The PCM must be reprogrammed. Replace the PCM. Is the replacement complete? | -- | Go to Step 17 | --

17

1. Use the scan tool in order to clear DTCs.
2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK