DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance. Buick Century (China) (CNG) 1999

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1999 🢒 Century (China) (CNG) 🢒 DTC 🢒 DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance

Engine Controls Components
HO2S, EGR and PCM (NF2 Only)
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM monitors the EGR valve pintle position input to ensure that the valve responds properly to commands from the PCM. The PCM compares Actual EGR Position with Desired EGR Position when the valve is commanded open. If Actual EGR Position is 15% less than Desired EGR position when the PCM is commanding the EGR valve opened, DTC P0404 will set.

Conditions for Running the DTC

•	No TP, IAT, MAP, MAF, ECT, CKP sensor, VSS, Misfire, Idle Speed, Fuel Injector DTCs set.

•	Engine coolant temperature is greater than 75°C (167°F).

•	Engine run time met. The time ranges from 20 seconds to 6 minutes depending upon engine coolant temperature at startup.

•	TP angle is greater than 2%.

•	Vehicle speed is greater than 2 mph (3.2 km/h)

•	System Voltage is between 10 volts and 18 volts.

Conditions for Setting the DTC

•	Actual EGR position is 15% less than Desired EGR Position.

•	The condition is present for longer than 25 seconds.

Action Taken When the DTC Sets

•	The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecuitive trip in which the diagnostic has been run and failed.

•	If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control, and the EBTCM will illuminate the TRACTION OFF lamp.

•	The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC

•	The PCM will turn OFF the MIL 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

Check for the following condition(s):

•	Excessive deposits on the EGR 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.

•	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 J 39200 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.

Refer to Intermittents and Poor Connections Diagnosis Connector Repairs and Wiring Repairs .

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

Verifies that the malfunction is present.

If DTC P0404 will only set under certain conditions, the malfunction may be intermittent, refer to Diagnostic Aids. If an intermittent wiring problem is not present, check for a poor connection at the PCM or the EGR valve.. If the connections are OK and DTC P0404 continues to set, replace 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.

DTC P0404 - EGR Valve Stuck Closed

Step

Action

Value(s)

Yes

Was the Powertrain OBD System Check performed?

Go to Step 2

Go to the Powertrain On Board Diagnostic (OBD) System Check

Important: : If any of the following DTCs are set, diagnose the other DTC first.

•	DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit

•	DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage

Turn on the ignition switch.
Select the scan tool EGR valve output control function.
Increment the EGR valve through all positions while comparing Desired EGR Position to Actual EGR Position.

Does Desired EGR Position remain close to Actual EGR Position at all commanded positions?

Go to Step 3

Go to Step 4

Review and record scan tool Fail Records data.
Operate the vehicle within Fail Records conditions.
Using a scan tool, monitor Specific DTC info for DTC P0404.

Does the scan tool indicate DTC P0404 failed this ignition?

Go to Step 4

Go to Diagnostic Aids

Disconnect the EGR valve.
Connect a J 39200 DMM to measure voltage between the EGR pintle position sensor ground circuit and the 5 volt reference A circuit at the EGR valve connector.

Is the voltage at the specified value?

5.0V

Go to Step 5

Go to Step 10

Probe the EGR pintle position signal circuit at the EGR valve harness connector with a J 35616-200 test light connected to battery positive voltage.

Is the J 35616-200 test light on?

Go to Step 8

Go to Step 6

Connect a jumper between the 5 volt reference A circuit and the EGR pintle position signal circuit at the EGR valve connector.
Observe Actual EGR Position on the scan tool.

Is Actual EGR Position at the specified value?

100%

Go to Step 9

Go to Step 7

Turn off the ignition switch.
Disconnect the PCM.
Check the EGR pintle position signal circuit for an open.
If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Step 17

Go to Step 15

Turn off the ignition switch.
Disconnect the PCM.
Probe the EGR pintle position signal circuit with a J 35616-200 test light to battery positive voltage.

Is the J 35616-200 test light on?

Go to Step 13

Go to Step 14

Check for poor terminal connections at the EGR valve.
If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Step 17

Go to Step 12

Check for the following conditions:

•	5 volt reference A circuit open between the PCM and the EGR valve.

•	5 volt reference A circuit shorted to ground.

If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Step 17

Go to Step 11

Check for the following conditions:

•	EGR pintle position sensor ground circuit open.

•	EGR pintle position sensor ground circuit shorted to voltage.

If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Step 17

Go to Step 15

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

Is the action complete?

Go to Step 17

Locate and correct the short to ground in the EGR pintle position signal circuit. Refer to Wiring Repairs .

Is the action complete?

Go to Step 17

Check the EGR pintle position signal circuit for a short to the EGR pintle position sensor ground circuit.
If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Step 17

Go to Step 16

Check the circuits related to the EGR valve for poor terminal connections at the PCM.
If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Step 17

Go to Step 16

Replace the PCM.

Important: : The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

Go to Step 17

Review and record scan tool Fail Records data.
Clear DTCs.
Operate the vehicle within Fail Records conditions.
Using a scan tool, monitor Specific DTC info for DTC P0404.

Does the scan tool indicate DTC P0404 failed this ignition?

Go to Step 2

System OK