Right before my 2000 4.0 Classic XJ had a check engine light, the dash displayed a 'rear hatch open' warning, which didn't seem accurate. The results from the CEL are P0443 with a recommendation of replacing the EVAP Control Purge Valve. The other note from the CEL said my battery voltage is at 12.45V, from what I understand normal operation is 13.8V.

Should I try to address the voltage issue before replacing the EVAP Purge Control Valve? Seems like an electrical issue may be involved.

Just to note, I recently upgraded my power and ground cables with K Suspension's ultimate power cables, as well as 4 port fuel injectors - been running great for hundreds of miles. I properly reset my ECM after the upgrades.

Any insight would be appreciated.

 

Probably a good idea to deal with the voltage problem first. Low voltage can make the computer modules go funny in the head and you are going to have to deal with that problem in any event. You can confirm voltage at the battery terminals with a multimeter.

P0443 can also be triggered by poor electrical connection on the purge valve or wiring problems.

 

Thank you for the reply.

My XJ now won't start, got extremely low voltage at the battery. I'm going to check all the grounds tomorrow. If it isn't the ground, it must be a bad battery, correct? Anything else I should consider?

 

You should probably have your battery and alternator load tested. The battery might be low because it's not charging properly. If you have a battery charger maybe see if it charges up OK. Obviously also make sure your battery terminals and cables are in good shape. That's gotten me in trouble before.

 

Do a parasitic load test, any draw over 30mA on your battery will flatten it, if a test light illuminates, that is more than enough

How old is the battery, and what has been its use cycle ?

A bad battery will hardly turn the starter, or just click the solenoid

 

Thank you for the reply.

If replacing the battery and EVAP purge canister doesn't resolve the issue, I'll look into parasitic draw.

 

Replacing the EVAP purge control valve, battery, and starter did not resolve the issue.

I now believe most of these issues are related to a bad ground.

The rear hatch dash warning light will stay lit when all the doors are closed, the light will go out if you manually press in the door sensor, as if the circuit is reversed.

I got a multi-meter and ran some basic tests, the voltage at battery from sleep, start, and running were within normal range.

I am going to get some sand paper, copper washers, and see if I can improve my grounds. Any other input would be appreciated.

 

UPDATE

I am able to clear the stuck rear hatch light by holding in the door sensor a few times. As if re-establishes the ground? I'm not sure.

I've read other posts with symptoms like these, one fix was replacing the auto shut down relay. Does anyone know where that lives?

 

ASD relay is in the underhood PDC, swap it with one of the other relays. easiest way to test it.

 

Thank you, I'll post what I find.

 

Turns out it was a bad ground. Cleaned all points with steel wire brush and added some copper washers. Everything is working like it should.