Mechanics

SERVICE ENGINE SOON LIGHT

2001 Buick Lesabre

Computer problem
2001 Buick Lesabre 6 cyl Front Wheel Drive Automatic 75000 miles

The service engine soon light was on. Code reader gave a P1404 code. I changed the EGR valve and cleared code. After driving for about 15 minutes I stopped the vehicle then restarted. Service light was back on. Car runs very good, no apparent performance problems. What is my next step?
Thanks, Earnest T
Avatar
Earnest T
February 10, 2008.



DTC P1404
Circuit Description
The powertrain control module (PCM) monitors the exhaust gas recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM. When the ignition switch is turned ON, the PCM learns the EGR learned minimum position. The PCM compares the EGR learned minimum position to the EGR position sensor when the EGR valve is commanded closed. If the EGR position sensor indicates that the EGR valve is still open when the PCM is commanding the EGR valve closed, this DTC will set.

Conditions for Running the DTC
The system voltage greater than 10 volts.

The EGR valve is enabled.

Conditions for Setting the DTC
EGR position sensor is 0.2 volts more than the EGR learned minimum position when the Desired EGR Position is commanded to 0 percent.
The above condition is present for 80 seconds.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
Inspect for the following condition: Excessive deposits on the EGR valve pintle or seat--Remove the EGR valve and check for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.

If the condition is intermittent, refer to Intermittent Conditions.

Test Description
The numbers below refer to the step numbers on the diagnostic table: This step verifies that the malfunction is present.

If DTC P1404 will only set under certain conditions, the malfunction may be intermittent. Refer to Diagnostic Aids. If an intermittent wiring condition is not present, test for a faulty connection at the PCM or the EGR valve. If the connections are OK and DTC P1404 continues to set, replace the EGR valve.

Step
Action
Values
Yes
No

Schematic Reference: Engine Controls Schematics

1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls

2

Important
If a DTC P0403 is set, diagnose that DTC first.

Install a scan tool.
Start the engine.
Use a scan tool in order to observe the EGR position sensor parameter.
Does the scan tool indicate that the EGR position sensor is at the specified value?
0 %
Go to Step 3
Go to Step 5

3
Turn ON the ignition, with the engine OFF.
Use a scan tool in order to command the EGR valve from 0 percent to 100 percent.
Does the Desired EGR Position remain within 15 percent of the EGR Position Sensor at all commanded positions?
--
Go to Step 4
Go to Step 6

4
Observe the Freeze Frame and/or 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 to the Freeze Frame and/or Failure Records data that you observed.
Does the DTC fail this ignition?
--
Go to Step 5
Go to Diagnostic Aids

5
Turn OFF the ignition.
Disconnect the EGR valve.
Turn ON the ignition, with the engine OFF.
Use a scan tool in order to observe the EGR position sensor parameter.
Does the scan tool indicate that the EGR position sensor is at the specified value?
0 %
Go to Step 6
Go to Step 9

6
Measure the voltage from the 5 volt reference circuit of the EGR position sensor to the ground circuit of the EGR position sensor.

Does the DMM display voltage near the specified value?
5 V
Go to Step 7
Go to Step 8

7

Important: If the fuse blows, locate and repair a short to ground in the signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Connect a fused jumper between the 5 volt reference circuit of the EGR position sensor and the EGR pintle position signal circuit of the EGR position sensor.

Does the scan tool indicate that the EGR position sensor is near the specified value?
100%
Go to Step 13
Go to Step 11

8
Measure the voltage from the 5 volt reference circuit of the EGR position sensor to a good ground.

Does the DMM display voltage near the specified value?
5 V
Go to Step 10
Go to Step 12

9
Test the EGR pintle position signal 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 17
Go to Step 14

10
Test the EGR position sensor ground 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 17
Go to Step 14

11
Test the signal circuit for high resistance or a high resistance short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 17
Go to Step 15

12
Test the 5 volt reference circuit of the EGR position sensor for an open, a short to ground, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 17
Go to Step 15

13
Inspect for poor connections at the harness connector of the EGR valve. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 17
Go to Step 15

14
Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 17
Go to Step 16

15
Replace the EGR valve. Refer to Exhaust Gas Recirculation (EGR) Valve Replacement.

Did you complete the replacement?
--
Go to Step 17
--

16
Replace the PCM. Refer to Diagnostic System Check - Engine Controls.

Did you complete the replacement?
--
Go to Step 17
--

17
Use the scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
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 18
Go to Step 2

18
Use a scan tool in order to 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

Dennyp
Feb 10, 2008.