Help! Bad ECM?

Hi Guys,

I picked up a 98 Cherokee a couple months ago, and after having it about a month had an electrical fire which fried part of the harness. I replaced the entire harness, engine and behind the dash. Now I'm having an issue where it won't idle, under light/moderate acceleration it surges and backfires. When given full throttle it runs fine. This doesn't happen all the time though, it can be running fine and then starts up. When it does it the check engine light comes on and throws a code for the upstream o2 sensor running high. I hooked the scanner up to it when it was going on and both o2 sensors were frozen, no change in volts. The front o2 was stuck at 0.7 and the rear at 0. Would this be caused by the ECM being damaged by the shorting out? When the xj is running fine both o2 sensors work as normal.

no ideas? I've tried replacing the tps and map sensor as well, but there was no change.

If you have a CEL light, download the exact trouble codes, Google them, and fix the faults. From the described symptoms, you have O2 sensor, O2 fuse, or O2 sensor wire harness issues.

PCM failure of any kind is very highly unlikely and usually results in not running at all, or persistent symptoms that do not happen only sometimes.

O2 sensor replacement is normal routine maintenance.