I just bought an 02 Accord 3.0 V6, in great shape. Has a P1491 code along with the 31-2 pfinh communication failure according to my Snap on scan tool. I'm assuming this is causing the TCS light and is linked to my P1491 code. After a lot of research on this site, I took off the upper intake and the EGR port wasn't too bad. Then took off the lower intake and the port from the top of the lower to the EGR valve was completely clogged. Removed both cleared everything out perfectly. New gaskets, reassembled. Drove a couple miles, in two trips, boom, code reappears. So now I'm looking at electrical issues from the PCM to the EGR valve. Does anyone have an ALLDATA pinpoint test or any advice at all? I've found a test for a 2000 but the wiring seems to be a little different. I have 9 volts at the power and ground on the EGR connector (#4 & #6). Seems high, I'm thinking I should have PCM voltage of around 5 volts. Anybody?

 

yes you should have a refrence voltage of 5 volts. seeing you have 9 i would say a loose ground somewhere. check the video scannerdanner has on egr testing.

 

Thanks, do you have a link? There are so many videos!

 

With the EGR 6P disconnected and engine idling you should read battery voltage between terms. 4&6. With engine off and ignition sw. in ON (II) you should read 5V between terms 2&3.

 

Ok this makes sense... On terminals 4 and 6 I have 9.5-10v I placed a load (3157 bulb with socket and pigtail) across them and not even a hint of a glow. There seems to be a good ground and the power wire (#4 pink) has continuity to PCM but it does have 7 ohms of resistance. Ill start checking for my open or damaged wire.

 

So I tested all the circuits and they are GOOD. Pulled the pink (EGR valve control input) wire at the ECM and have the same 9.5-11 Volts. Tried to load test the circuit at that ECM and have no illumination, just a little buzz. Reasssembled everything and I still have the tely code. It pops up as a one trip code almost immediately. And as a hard code within 2 minutes of driving on the second trip. I'm at a complete loss. I guess I'm just having a hard time accepting that the ECM could be bad after finding the intake clogged up and they just don't go bad that often, and when they do the car is completely dead.

 

test for reference volts at the map sensor connector on all three pins with the ignition on with the car off..you should get 4.5-5 volts on one of em

 

JKyleP,

Ever figure this out? I have a very similar yet slightly different problem on my 01 Accord v6 that I cannot get to resolve...yes, after cleaning out the EGR port! My friends think its the pcm, but I'm not convinced quite yet.

 

I did figure it out. When I bought the car it had a fairly new EGR valve on it and the resistance values were all good and the valve opened fine with power applied. The lift sensor voltage at the PCM showed approximately 1.2 volts at the PCM which it should read when the valve is closed. Before putting in a new PCM I used the graphing function on my scan tool one last time and voila, voltage was randomly falling to zero, I verified it was at the valve lift sensor (on top of EGR valve) by tapping it with a screwdriver handle while the car was running and I watched sensor voltage value drop from 1.2v to 0.01v and back again. Stupid Chinese EGR valve. I'm glad I had the graphing capability and I'm glad I checked twice instead of buying a PCM. I would definitely check this avenue before spending $500+ on a PCM and programming.

 

I figured mine out finally. I replaced the EGR valve which took care of the insufficent lift code. A disconnected PCV hose was causing a vacuum leak and causing an IACV and TPS code, as well as TCS light dash light. Corrected the vacuum leak and it all went away.