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DTC P0402: Exhaust Gas Recirculation (EGR) Flow Excessive
The engine control module (ECM) tests the exhaust gas recirculation (EGR) flow when the EGR is in operation. EGR desired flow is compared to EGR actual flow. If EGR flow is higher than expected DTC P0402 will set.
Code P1491 in Honda/Acura vehicles means insufficient EGR valve lift. Note - this is not the same as 0401 for EGR low flow when you have to clean EGR passage in the intake manifold. If code 1491 is not accompanied with 0401 - that could be faulty EGR valve itself. Try to reset the code, and if it will return soon - replace EGR valve. If, however you see both codes together - cleane the manifold passage before you replacing the valve.
This is not a cut and dry fault code. This means that more than one thing wrong can set the code in the computers memory. Here is the low down on the P0402 fault code. This is from the OBD2 fault code diagnostic book.
P0402 - Exhaust Gas Recirculation Flow Excessive Detected
- Engine Light ON (or Service Engine Soon Warning Light) - Possible engine hesitation
- EGR solenoid valve harness is open or shorted - EGR solenoid valve circuit poor electrical connection - EGR volume control valve stuck closed - Dead (Weak) battery - Faulty EGR temperature sensor and circuit - Faulty EGR Valve - EGR passage clogged - Exhaust gas leaks
P0171 - is fuel system is to lean (Bank#1) Take the car back to who ever scanned it for you and see if any codes are now pressent in particular to the EGR Valve they range from P0400 up to and including P0409, or any other new codes.While you are at it make sure they erase the set code P0171 un less it is already don.If no codes show up on the new scan replace the Ignition Control Module not the ( ECM -on board computor).If new codes do show up follow up on them first. Good Luck.
P0409....Exhaust Gas Recirculation Sensor
'A' Circuit Changing the EGR valve most likely will solve the problem. This website will explain it a lot better than i can. http://www.aa1car.com/library/egr.htm Good luck hope this helps
just because the check engine light is back on, it doesn't necessarily mean it is for the same problem. it could be, but would need to pull codes again to find out what its for. literally hundreds of different codes could turn on check engine light. also, was original code for "insufficient egr flow" or "excessive egr flow"? it makes a difference.
EGR flow is monitored by the PCM by it looking for a reaction in the FRONT O2 sensor in responce to the command given to the EGR valve. The linear electronic EGR valve sends a return signal to the PCM indicating the relative position of the step motor and hence how far open (or closed) the EGR valve is in responce to the PCM command. The PCM expects to see (within a set of given parameters) a change in the O2 sensor reading (change in exhaust gas make up) after the EGR valve is commanded open or closed. If it doesn't, or that change is not within the expected parameters, a code will be set based on the skewed data. Generally a "insufficient flow" code will be set by:
1.Faulty EGR valve (sticking, or "lying" to the PCM about the actual valve position) 2.Faulty electrical connection at the EGR valve (causing false data) 3.Clogged EGR passages 4. Bad read from the MAP, or TPS, causing the PCM to misinterpret the EGR data based on faulty operational data from the other sensors 5. (Very rarely) A marginally "slow" O2 sensor. (PCM does not "see" the change in exhaust make up quick enough and interprets that as poor EGR flow.)I have found that normally this code means that the EGR is not opening the amount that it has been commaneded to by the PCM. Normal cure for me lately has beed to repalce the EGR valve and to clean out the passages while the valve is off. The Tech 2 is able to command the EGR open and show the commanded opening and the actual opening. When this code is present the actual and commanded do not match closely at all.Thanks for using FixYa - a FixYa rating is appreciated for taking the time to answer your FREE question.