Circuit Description
This diagnostic checks for an exhaust gas recirculation (EGR) valve that is stuck open. The powertrain control module (PCM) checks for a stuck open valve when the desired EGR position is at 0 percent. The PCM determines that the EGR valve is stuck open if the actual EGR position and the learned closed EGR position vary by more than a predetermined value. The PCM attempts to clear any obstructions from the valve. To clear the obstruction the PCM waits for the EGR desired position to be more than 20 percent. Once the desired EGR position is more than 20 percent the PCM commands the EGR valve to 100 percent then back to 0 percent. The PCM does this three times. The PCM rechecks for a stuck EGR valve when the desired EGR position returns to 0 percent. A failure counter increments if the stuck EGR valve condition is still present. This DTC sets when the counter reaches a predetermined value.
Conditions for Running the DTC
The ignition voltage is more than 11.7 volts.
Conditions for Setting the DTC
The actual closed EGR pintle position voltage is 0.29 volts more than the desired closed EGR pintle position voltage.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and the Failure Records. |
| • | The PCM disables the EGR valve for the ignition cycle. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
Important: An intermittent EGR pintle position signal circuit causes this DTC to set.
Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.If you are using the scan tool to control the EGR solenoid and are unable to increase or decrease the EGR position, inspect the EGR control circuit for a short to voltage.
Using the Freeze Frame and Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed. For an intermittent condition, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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If DTC P1635 sets at the same time, this indicates that the 5 volt reference circuit is either shorted to a ground or shorted to a voltage. The 5 volt reference circuit is internally connected within the PCM.
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This step tests for an open EGR valve when the valve should be closed.
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This step tests for an EGR pintle position voltage that is out of range. The EGR pintle position voltage should be between 0.14 and 1.07 volts at idle.
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Using Freeze Frame and Failure Records data may aid in locating an intermittent condition.
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This tests whether the ground circuit is available to the EGR valve. Inspect for poor electrical connections at the EGR valve. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
|
Important: Inspect the EGR pintle position signal circuit for an intermittent condition before proceeding with this diagnostic table. An intermittent condition with the signal circuit causes this DTC to set.
Did DTC P1635 fail this ignition? | -- | |||
Idle the engine. Is the idle quality poor? | -- | |||
4 |
Does the idle quality return to normal? | -- | ||
Is the EGR pintle position voltage within the specified range? | 0.14-1.07 V | |||
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Diagnostic Aids | ||
7 |
Is the EGR pintle position voltage below the specified value? | 0.14 V | ||
Probe the EGR pintle position ground circuit at the EGR valve harness connector with the test lamp connected to B+. Does the test lamp illuminate? | -- | |||
9 | Measure the voltage at the 5 volt reference circuit to ground using the DMM . Refer to Measuring Voltage in Wiring Systems. Is the voltage greater than the specified value? | 5.1 V | ||
10 |
Did you find and correct the condition? | -- | ||
11 |
Did you find and correct the condition? | -- | ||
12 |
Did you find and correct the condition? | -- | ||
13 |
Did you find and correct the condition? | -- | ||
14 | Repair the 5 volt reference circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
15 |
Did you find and correct the condition? | -- | ||
16 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Is the action complete? | -- | -- | |
17 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
18 |
Does the scan tool indicate that this test ran and passed? | -- | ||
19 | Select the Capture Info option and the Review Info using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
