Problems with Multiple Codes after Exhaust Change (1 Viewer)

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Aug 26, 2009
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Annapolis, Maryland
 
 
I have been helping my father with his '94 to no avail.

He purchased an aftermarket exhaust that eliminated a cat and had a local mechanic and friend of the family install it. He had two new Toyota O2 sensors installed with it.

After installation, it immediately started throwing O2 sensor codes (27 I think?). We did a resistance check on the sensors and they seemed to be fine. We swapped in the old ones and the codes persisted.

I cleared the codes and the truck ran at ran fine for half a tank. CEL returned but the codes then included a 71 for EGR.

I cleaned up the connectors to the O2 sensors and cleared the codes again. The O2 codes disappeared for a short time, but the returned with completely new codes 25 and 28 for a lean mixture. It never stops!

And to throw another variable into the mix, my father had a piece of wood wedged between the wiring harness and the EGR pipe to insulate it against the heat. He removed it around this time and there is visible damage to the wrap around the harness near the EGR tube.

We're kind of at our wits end here. Our mechanic friend thinks it is possible he fouled the O2 sensors with penetrating oil during installation, so I was thinking about ordering some Densos just to try it out. If that didn't work, I was going to cut the wrap off the harness near the EGR to inspect the wires.

Advice? We could really use some direction here as we are a bit stumped.
 

94SRUNNER

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Dayton, OH
 
 
I would certainly take a very close look at the harness by the EGR system. That can be susceptible to damage form heat and block of wood certainly doesn't help. There are some good tips for re-wrapping the harness in this location. And of course inspect for damage while things are disconnected and unwrapped.

As far as the O2 sensors. How does the wiring harness leading up to the the O2 sensors look? Any damage when the shop did the removal and installation of the new aftermarket unit? Also you my want to pull them and check them for any possible physical damage. Make sure to test the O2 sensors according to the FSM trouble shooting guidelines.
 
Joined
Feb 25, 2009
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Richmond, VA
How far are you from Richmond?

If it is a 94 and ODBI you can disable the EGR for good and not have to worry about it anymore.
Do a search and you will find out how to disable that thing its simple, they are useless.
As said above check harness and all O2 wiring as well.

Good Luck
 
Joined
Aug 26, 2009
Messages
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Location
Annapolis, Maryland
 
 
As far as the O2 sensors. How does the wiring harness leading up to the the O2 sensors look? Any damage when the shop did the removal and installation of the new aftermarket unit? Also you my want to pull them and check them for any possible physical damage. Make sure to test the O2 sensors according to the FSM trouble shooting guidelines.
I have pulled the O2 sensors and inspected them for damage. They test as functional per the FSM, and the wiring and connectors for both O2 sensors look good.
 
Joined
Aug 26, 2009
Messages
2,915
Location
Annapolis, Maryland
 
 
How far are you from Richmond?

If it is a 94 and ODBI you can disable the EGR for good and not have to worry about it anymore.
Do a search and you will find out how to disable that thing its simple, they are useless.
As said above check harness and all O2 wiring as well.

Good Luck
I'm in the Manassas area and my father is in the Warrenton area. Not terribly far. Don't know how my father would feel about disabling part of the emissions on his truck :p
 

94SRUNNER

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Dayton, OH
 
 
Since the O2 sensors checked out, I would dig into the wiring harness by the EGR and start looking for damage.

Did you inspect all of the wiring associated with the O2 sensors?
 

94SRUNNER

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Oct 9, 2006
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Dayton, OH
 
 
Well it seems as if the next step as I mentioned above, is to inspect the wiring harness by the EGR. Just take your time and be careful.
 
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