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Intermittent 21 code.

Tacowhip

NAXJA Forum User
Location
New Jersey
Hey guys. I’m getting an intermittent 21 code, Oxygen sensor. It’s been throwing this code ever since I’ve bought the Jeep 3 years ago. I replaced it with an NTK. Still throwing the code. Any body have any information on this issue, or a wiring diagram, possible fuses? There’s also a 12 code that’s always there. Rarely do I disconnect the battery. It’s a 95 sport 4.0. Thanks.
 
Have a good look at the wiring and make sure it's not hitting the exhaust and shorting out. If it's not secured well, it can melt against the exhaust manifold.
 
Check the O2 harness where it exits the end of the square plastic wire harness tube that is near to exhaust tube #1. Often a previous mechanic will route the O2 sensor wire too
near to the exhaust tube and fry the wires, and then perform a dodgy repair. Open up
the black plastic corrugated split cover (wire harness) starting at this point and follow it
down to the sensor. Inspect for anything that looks stupid, or out of the ordinarily.

This happened on my car. After months of fiddling around, and 3 new O2 sensor$, I checked
the wires there and found a wire harness repair done by a previous owner using Romex
home wires and non-insulated crimped connectors! All was good after correcting this with
proper wires, and twisted & soldered splices, and double layers of heat shrink tubing.
 
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