Questioni have a 2001 oldsmobile silhoutte 3.4 v6. i have a service engine soon light on. the code is p0403. i changed the egr valve. also the cat conv. and all pipes,and resignator, i can put the light out and codes to 0, however on the next start the light snd p0403 code returns. what do you think i should try?
AnswerHi
Seeing as how it returns so quickly, I would think you have either faulty wiring going to or from the valve, or you have got a bad valve.
I would REALLY suspect the wiring issue first.
Here is the GM diagnostic tree, if needed.
I hope it helps
Pawl
Step
Action
Yes
No
2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, command the EGR from 0 percent to 100 percent.
Does the EGR position sensor remain close to the Desired EGR Position at all Commanded positions?
Go to Step 3
Go to Step 4
3
Observe the Freeze Frame/Failure Records data for this DTC.
Turn OFF the ignition for 30 seconds.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, or as close the Freeze Frame/Failure Records data that you observe.
Does the DTC fail this ignition?
Go to Step 4
Go to Intermittent Conditions
4
Turn OFF the ignition.
Disconnect the EGR.
Turn ON the ignition, with the engine OFF.
Probe the EGR Solenoid High Control circuit with a test lamp connected to a good ground.
With a scan tool, command the EGR between 0-10 percent.
Does the test lamp turn ON and OFF with each command?
Go to Step 5
Go to Step 6
5
Connect a test lamp between the high control circuit of the solenoid and the low control circuit of the solenoid.
With a scan tool, command the EGR between 0-10 percent.
Does the test lamp turn ON and OFF with each command?
Go to Step 10
Go to Step 9
6
Does the test lamp remain illuminated with each command?
Go to Step 8
Go to Step 7
7
Test the EGR Solenoid High Control circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 14
Go to Step 11
8
Test the EGR Solenoid High Control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 14
Go to Step 11
9
Test the EGR Solenoid Low Control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 14
Go to Step 11
10
Inspect for poor connections at the harness connector of the EGR valve. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring systems.
Did you find and correct the condition?
Go to Step 14
Go to Step 12
11
Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 14
Go to Step 13
12
Replace the EGR valve. Refer to Exhaust Gas Recirculation (EGR) Valve Replacement .
Did you complete the replacement?
Go to Step 14
--
13
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?
Go to Step 14
--
14
Use the scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?
Go to Step 15
Go to Step 2
15
With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?
Go to Diagnostic Trouble Code (DTC) List
System OK
