Manager Forum

Customer has this 96 Honda Accord with a 285,000 miles on it. Car has 2.2L engine with auto trans. Runs great, drives nice and no other issues other than this one. Issue is the PCM has a P1491 (EGR System) codein it that keeps coming back after it leaves the shop. I can have it here, do a diagnosis as per on Demand , nothing shows up. Customer can take the car and within several hours of driving the CEL comes back on and we got this P1491 code again. Frustrating. Is there something I need to do differently? Do I simply replace the EGR valve and hope that fixes it? Is it an intermittant PCM issue? Need answers.

is it a v tech engine? i wouldn't throw an egr at it. possibly an amplifier or really clean out the ports. i've had rare occasions where the cat's have had slight restrictions that effected the egr system. i don't know if it applies on this one but i know the operating temperature is critical. i would also look carefully at the vac hoses. this system has a few vac relays that control egr. i find a lot of hoses cracked where they attach to the steel tubing.

Almost always EGR ports plugged for this code. Check all EGR ports.

ricmorin wrote:Almost always EGR ports plugged for this code. Check all EGR ports.

What dat guy Ric said, we see it all the time.

John C. wrote:

ricmorin wrote:Almost always EGR ports plugged for this code. Check all EGR ports.

What dat guy Ric said, we see it all the time.

Vehicle is coming in later this week an I'll be sure to check these ports for restriction.

Thanks guys for the input. It is greatly appreciated. Will post what the fix is.

not sure if this applies on this particular vehicle but i run a piece of e/brake cable attached to a drill into the ports to clean them.

The odysseys are the ones I get alot of egr port blockage. Never had an accord with one. Id upsell a bg decarb if I found blockage. It really works well

Ok. I got this car in today an we took the EGR valve off. Valve and ports are clean and open no problem. EGR valve opens nicely when vacuum is connected to hose port. However, EGR position sensor stays fixed on 3.49 volt with vacuum or without vacuum to the valve. To me, even though On Demand does not give me any testing for the sensor, it seems that the sensor is bad. Am I right or wrong? And it appears that the sensor is part of the valve.

Comments?

Mark (tech in our shop) says, if you are 100% sure the ports are all clean, then it's the EGR valve, I guess that sensor is part of it?? What do I know? I just answer the phones.

agreed with the replacement of the egr. however, i would make sure that the ports are clean. not just visually but i would run the ports. is the sensor receiving enough vacuum. you mentioned it functioning with vacuum pump but i've seen situations where the engine wasn't supplying enough vac to the valve. those vac hoses have a habit of cracking where they attach to the tubing and it's so minor that sometimes it's a s.o.b. to find. i had one that was acting up only during low vac situations such as long hills. i finally replaced all the associated vac lines and it solved the problem. if the e.g.r valve doesn't cure it run a vac gauge in line and see what the vac reading is while driving.

Well steve, ........... you do present some interesting feedback. I just got the new egr valve and will install it and see what happens. Regarding cleaning the egr ports, this engine is clean, clean, clean. When I look in the egr engine ports with my boroscope I can see right into the heart of the engine. No carbon buildup - nothing. Zilch. We got vacuum to the valve so I conclude the only thing left is the egr valve to replace beings that the position sensor voltage never changes wit ht e valve open or closed.

The fix for this Accord was a new EGR valve. It now sends correct voltage sensor signals to the PCM and so far (several hundred miles) the PCM is happy.

Thanks to the Forum members for the help!