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Old 10 Oct 2009, 10:16 pm
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Default 99 Honda Odyssey code p1491 and transmission shifts rough?

I have a 99 Honda Odyssey with a code P1491 and a code P1491 Pd. They are the same code but one says Pd after and I don't know what that means. The code means EGR Valve insufficient. I'm guessing that the EGR valve needs replaced. If it is something else please let me know. The car seems to have to no mechanical problems beside the transmission shifting a little rough at times. Also where is the EGR valve located on this vehicle? The other problem I'm having with the van is that the traction control light comes on periodically and stays on until the car is turned off. When the light is on the transmission sometimes shifts rough. The RPMs go up to around 4000 RPMs and then it shifts roughly into the next gear. If anyone can help me out with these problems that would be great. If you need any more details just ask.
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Old 10 Oct 2009, 10:31 pm
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Join Date: Aug 2007
Posts: 1,338

everything may be related to the EGR operation. Honda had a service bulletin out on this car for the problem with the EGR. In most cases, it goes deeper than just replacing the EGR valve. The problem is that the port that the EGR flows through gets clogged with carbon and that causes the insufficient flow of recirculated exhaust gas through the EGR.

the EGR valve is under the cover for the intake plenum on the top of the engine. however, to clean the port you need to remove the plenum. Honda has a repair kit available that has all the parts you need to do the job.

the issue with the TCS light is that the lack of EGR causes a reduction of engine power. The TCS works by reducing engine power until tracktion is restored, so when the TCS control unit sees the reduction in engine power it gets fooled into thinking the car is in TCS mode and puts the TCS light on. once the light is on, it will remain on until the ignition is shut off and turned back on. so that sounds related to the EGR.

the transmission shift may or may not be related. an engine that isn't running right will cause the trans to act abnormally. so before you do anything with the trans, replace the EGR and have the port cleaned and the kit installed. then, if the trans still shifts high you can decide what to do at that point.

I would go suggest you go to a honda dealer and get the parts and a copy of the bulletin that shows how to install them. if it looks beyond your abilities, then pay the dealer to do it or find another shop that you use to do it.

hope that helps
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