Newer Jeep issue - need help

[Eagle]

A friend of mine has a 1999 Wrangler. It started out as a 4-cylinder 5-speed. Late last year he swapped in the complete power train and wiring harness from a 2000 Wrangler 4.0L 5-speed. It now runs and drives okay -- he uses it for plowing his house and his shop's parking lot -- but he has a check engine light. The codes indicate that BOTH O2 sensors are bad.

 

The check engine light was not on in the Wrangler the "new" engine care out of before he pulled it. And it seems unlikely that both O2 sensors could have been damaged in the engine swap. Does n anyone have any ideas? We're in Connecticut, so if he can't get this fixed he won't be able to renew the registration because it won't pass emissions testing with a check engine light fault showing.

[acfortier]

Did the O2 sensors differ for a 1999 2.5L vs. 2000 4.0L? Does seem unlikely that both went bad.

[FrankTheDog]

It is a 22 yr old vehicle and if the O2 sensors haven’t been replaced they could’ve been disturbed in the swap.

 I personally would change them out for a set of oem sensors and see what happens. Or take it to an emissions or exhaust specialist.

[gogmorgo]

What codes specifically? Not all O2 sensor codes indicate replacement, but it’s pretty common to see someone see an O2 sensor code and think that. Could be as simple as something having been left unplugged, or a pinched wire or something. Especially if the code comes back immediately after being cleared on a cold engine, before it’s had a chance to warm up and run all the monitor cycles it’s most likely to be an electrical fault.

[Pete M]

have the sensors been tested?

[JMO413]

Can you look at the sensors on the scanner you pulled the code with?

[jdog]

Have you checked the fuses