Circuit Description
The PCM monitors the EGR valve pintle position input to ensure that the valve responds properly to commands from the PCM. The Linear EGR valve is controlled by using an ignition positive driver and ground circuit within the PCM (control circuit). The driver has the ability to detect an electrical malfunction in the ignition positive or ground circuit. If an electrical malfunction occurs, the driver signals the PCM to set DTC P0403.
Conditions for Running the DTC
| • | No TP, VSS, Misfire, IAT, MAP, Idle Speed, Fuel Injector, ECT, CKP, or MAF sensor DTC(s) set. |
| • | System voltage is between 10 volts and 16 volts. |
Conditions for Setting the DTC
| • |
| The PCM detects an electrical malfunction in the control circuit for the EGR valve. |
| • | The above condition is present for more than 20 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 disable EGR for the ignition cycle. |
| • | 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. |
Diagnostic Aids
| • | Poor connection at PCM or EGR Valve. |
| 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, connect a DMM and check circuit continuity while moving connectors and wiring harnesses related to the EGR valve. A change in the display will indicate the location of the malfunction. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Verifies that the malfunction is present.
-
If DTC P0403 will only set under certain conditions, the malfunction may be intermittent. If an intermittent wiring problem is not present, check for a faulty connection at the PCM or the EGR valve.
-
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.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
With the engine idling, observe Actual EGR Position on the scan tool. Is Actual EGR Position at the specified value? | 0% | |||||||
Does Desired EGR Position remain close to Actual EGR Position at all commanded positions? | -- | |||||||
Does the scan tool indicate DTC P0403 failed this ignition? | -- | Go to Diagnostic Aids | ||||||
5 |
Is the test lamp ON with the commanded EGR valve position at 100%? | -- | ||||||
6 | Probe the EGR valve ground circuit at the EGR valve harness connector with a test lamp to B+. Is the test lamp ON? | -- | ||||||
7 | Probe the EGR valve control circuit at the EGR valve harness connector with a test lamp to B+. Is the test lamp ON? | -- | ||||||
8 |
Was a problem found? | -- | ||||||
9 |
Is the test lamp ON? | -- | ||||||
10 |
Was a problem found? | -- | ||||||
11 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Did you complete the repair? | -- | -- | |||||
12 | Locate and repair the short to voltage in the EGR valve control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||
13 |
Is the test lamp ON? | -- | ||||||
14 |
Is the test lamp ON? | -- | ||||||
15 |
Was a problem found? | -- | ||||||
16 | Locate and repair the short to voltage in the EGR valve ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||
17 |
Was a problem found? | -- | ||||||
18 | Locate and repair the short to ground in the EGR valve control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||
19 |
Was a problem found? | -- | ||||||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the repair? | -- | -- | ||||||
21 |
Does the scan tool indicate DTC P0403 failed this ignition? | -- | System OK |
