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Ask Chad Farhat Your Own Question
Chad Farhat
Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems
Category: GMC
Satisfied Customers: 3480
Experience:  Owner at Carolina Auto Service &Sales , 20 years Experience in Foreign & Domestic vehicles
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I have a 2004 GMC with a 6.6 Duramax diesel code p1404 egr 2

Customer Question

I have a 2004 GMC with a 6.6 Duramax diesel code p1404 egr 2 position error/egr- closed performance
Submitted: 8 months ago.
Category: GMC
Expert:  Chad Farhat replied 8 months ago.

Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.

Expert:  Chad Farhat replied 8 months ago.

hey how are you

i sent you 4 diagrams showing the test needs done to determine is it : is it a stuck open egr vent solenoid ,restricted exhaust causing high pressure , egr vacuum control etc...

The content of this article/image reflects the changes identified in TSB:06_06_04_022 Dated 04/12/2006

DTC P1404 CIRCUIT DESCRIPTION The exhaust gas recirculation (EGR) valve is vacuum operated. Vacuum for the EGR valve control system is supplied by a belt driven vacuum pump. The EGR valve vacuum control solenoid and the EGR valve vacuum vent solenoid work together to control the position of the EGR valve. The engine control module (ECM) monitors the EGR vacuum sensor signal to determine the amount of vacuum that is applied to the EGR valve. The ECM uses the mass air flow (MAF) sensor to calculate the amount of exhaust gas that is consumed by the engine. When the EGR valve is opened, the MAF rate will decrease. If the EGR vacuum sensor signal is higher than desired and the MAF rate is lower than expected, it is assumed that the EGR valve is not closing due to a vacuum problem and DTC P1404 sets.

CONDITIONS FOR RUNNING THE DTC - DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0405, P0406, P0489, P0490, P0500, P0651, P2142, P2144, P2144, and P2145 are not set. - The EGR valve vacuum control solenoid has been commanded to more than 70 percent. - The PCM is not in the Reduced Engine Power mode. - The BARO parameter is more than 72 kPa. - The Engine Speed parameter is between 610-820 RPM and is steady within 50 RPM for more than 3 seconds. - The ECT Sensor parameter is between 60-100°C (140-212°F). - The Calculated Fuel Rate parameter is between 3-20 mm(3). - The power take off (PTO) is disabled, if equipped. - The IAT Sensor parameter is more than 0°C (32°F). - The APP Indicated Angle parameter is less than 1 percent. - The Ignition 1 Signal parameter is between 11-18 volts. - The Vehicle Speed Sensor parameter is less than 0.40 km/h (0.25 mph). - The Engine Run Time parameter is more than 5 seconds. - All of the above conditions are met for more than 3 seconds. CONDITIONS FOR SETTING THE DTC - The ECM detects a higher than desired EGR vacuum sensor signal and a lower than expected MAF rate. - The above conditions are met for more than 4 seconds.

ACTION TAKEN WHEN THE DTC SETS - The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. - The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the 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 conditions: - A stuck open EGR vacuum vent solenoid. - A stuck open EGR valve vacuum control solenoid. - Proper vacuum line connections. - A restriction in the exhaust system causing high back pressure.

TEST DESCRIPTION

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Steps 1-2

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Steps 3-4

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Steps 5-9

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Steps 10-11

The numbers below refer to the step numbers on the diagnostic table.
3. The EGR vacuum vent solenoid is normally closed. When the EGR vacuum vent solenoid is closed, it will vent to atmosphere. Therefore it should not hold vacuum with this test.
4. The EGR valve vacuum control solenoid is normally closed. When vacuum is applied to the commanded open EGR vacuum vent solenoid it should hold vacuum. If the vacuum does not hold, then a stuck open EGR valve vacuum control solenoid is indicated.

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Chad Farhat
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Customer: replied 8 months ago.
I changed the the egr- it is vacuum operated and it came with actuator when I control it with my scanner It Moves In and Out
Expert:  Chad Farhat replied 8 months ago.

1-ok, that is good on egr ,so that is functioning when commanded ?

2-but is functioning when it needs to function? is the pcm controlling the solenoid when needed ? I sent you the EGR circuit digarma and the connection to the PCM

if you confident the egr system is working move to the exhaust restriction inspection

3- i sent you egr vacuum routing and components , check if routed correctly ,

4- this the EGR system description operation , please review

EXHAUST GAS RECIRCULATION (EGR) SYSTEM DESCRIPTION The exhaust gas recirculation (EGR) system is used to reduce the amount of nitrogen oxide (NOx) emission levels caused by combustion temperatures exceeding 816°C (1,500°F). It does this by introducing small amounts of exhaust gas back into the combustion chamber. The exhaust gas absorbs a portion of the thermal energy produced by the combustion process and thus decreases combustion temperature. The EGR system will only operate under specific temperature, barometric pressure and engine load conditions in order to prevent driveability concerns and to increase engine performance. The EGR system consists of the following components: EGR Valve The EGR valve is vacuum operated. The EGR valve is used to transmit exhaust gases from the exhaust system to the intake manifold to be recirculated into the combustion process. Vacuum Pump Vacuum for the EGR vacuum control system is created by a belt driven mechanical pump called a vacuum pump. When the engine is running, the vacuum pump is operating at all times. EGR Valve Vacuum Control Solenoid The EGR valve vacuum control solenoid is located in the EGR vacuum control system between the vacuum pump and the EGR vacuum vent solenoid. The ECM pulse width modulates (PWM) the ground path of the EGR valve vacuum control solenoid allowing metered vacuum from the vacuum pump to open the EGR valve to the desired position. The EGR valve vacuum control solenoid is supplied ignition voltage through the ignition 1 voltage circuit from the Fuel HT fuse. The EGR valve vacuum control solenoid is normally closed. EGR Vacuum Vent Solenoid The EGR vacuum vent solenoid is located between the EGR valve vacuum control solenoid and the EGR vacuum sensor. The ECM opens the EGR vacuum vent solenoid, allowing vacuum from the vacuum pump to build in the EGR vacuum control system. When the EGR vacuum vent solenoid is commanded closed, the EGR vacuum control system is vented to atmosphere which will cause the EGR valve to close very fast. The ECM controls the EGR vacuum vent solenoid by switching the ground path ON and OFF. Ignition voltage is supplied through the ignition 1 voltage circuit from the Fuel HT fuse. The EGR vacuum vent solenoid is normally closed. EGR Throttle Valve Vacuum Control Solenoid The EGR throttle valve vacuum control solenoid is located in the EGR vacuum control system between the vacuum pump and the EGR throttle valve. The ECM opens the EGR throttle valve vacuum control solenoid, allowing vacuum from the vacuum pump to close the EGR throttle valve. Diesel engines do not create enough engine vacuum on their own to allow the EGR gases into the combustion process. The EGR throttle valve, when closed, creates a restriction of incoming fresh air to the engine in order to create engine vacuum. When the ECM commands the EGR valve to open, the EGR throttle valve will be commanded closed. The ECM controls the EGR throttle valve vacuum control solenoid by switching the ground path ON and OFF. Ignition voltage is supplied through the ignition 1 voltage circuit from the Fuel HT fuse. The EGR throttle valve vacuum control solenoid is normally closed. EGR Vacuum Sensor The EGR vacuum sensor is located in the EGR vacuum control system between the EGR vacuum vent solenoid and the EGR valve. The ECM uses the EGR vacuum sensor to monitor the amount of vacuum that is available to the EGR valve. The ECM will make adjustments to the EGR vacuum control system in order to obtain the vacuum level necessary to achieve the proper EGR valve position. The EGR vacuum sensor is interfaced with the ECM by a 5-volt reference circuit, a low reference circuit and a signal circuit. MAF Sensor The MAF sensor is located in the air intake system between the air filter and the EGR valve out-take port. The ECM monitors the Mass Air Flow (MAF) sensor signal to calculate the actual amount of EGR flow into the intake manifold. When the EGR valve is opened, the MAF rate will decrease. When the EGR valve vacuum control solenoid is operated at 50-70 percent duty cycle, the MAF rate should drop at least 4 g/s. EGR Valve Cooler The EGR valve cooler is mounted on the right intake manifold, between the EGR valve and the exhaust pipe. Engine coolant flows through the EGR valve cooler in order to lower the exhaust gas temperatures before it enters the EGR valve and intake manifold. ECM The PCM calculates the amount of EGR needed based on the following inputs: - The accelerator pedal position (APP) sensor - The barometric pressure (BARO) sensor - The boost sensor - The engine coolant temperature (ECT) sensor - The exhaust gas recirculation (EGR) vacuum sensor - The intake air temperature (IAT) sensor - The mass airflow (MAF) sensor - The vehicle speed sensor (VSS) - The engine speed

2- Next Check the exhaust system ,did you check for restriction ?

Expert:  Chad Farhat replied 8 months ago.

hey ,just checking on you & see if you need additional help on it

Please let me know if you need anything else on it, just reply back and we will continue
A 5 Star Rating is much Appreciated
Please keep in mind that when you rate me , it does not end our conversation.
you can always come back to this conversation and ask me any follow up question you may have on this issue
(you can copy this link page & paste it in your browser when ready and it will open up our conversation again)
Thank You
Chad Farhat
ASE Certified Technician