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2000 XJ purchased on e-bay Diagnostic Codes

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Reader

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Neophyte to working on cars,in NJ/PA
I am a newcomer to workng on cars and to purchasing a used car on e-bay. I hope the sinking feeling in my stomach is premature.

I just got back from taking it to the inspection station. It failed for emissions problems.

They advised the check engine light does not work and it produced three codes:

P1491

P1491 Radiator Fan Control Relay Circuit An "open" or "short" circuit detected in the Electric Radiator Fan Control Relay circuit

I know there was a recall to install a fan shield on this model. Mine still needs it.

P0303

P0301 - P0304 Cylinder Misfire Misfire condition detected in cylinder #1/2/3/4

and

P0305

P0305/P0306 Cylinder Misfire Misfire condition detected in cylinder #5/#6


Is this an indication the cylinder head might be cracked? It does not seem to run rough, but perhaps the idle is very slightly high.

How about just a little SeaFoam and all will be well?

What is your best guess as to what is the matter with it? What should I do first? How do I get the check engine light working again. I guess first thing is to check the fuses?

Thank you
 
Last edited:
I'm no expert myself, but i can try :looney: . The missfire could be caused by hundreds of different things, but also by gunky spark plugs, which would be a very easy fix! New plugs are very inexpensive, and puttin them on is relatively simple as well, I just reccomend you go buy a Hanes automotive repair manual (they explain everything extremely well, with pictures). I hope that helps, good luck!
 
i have had cylinder misfires before and it was due to bad spark plugs

it is always a good idea to start a baseline with a new vehicle - ie fluids, oil- tune up etc and before diagnosing a bad head i would definatly tune it up, fix the fan problem and run some lucas fuel injection cleaner through or similar and see if that helps

also due to the cylinder misfires and the poor combustion of your gasoline you might have clogged your cat with unburnt carbon - mine got so bad it turned red hot and starting spitting out hot chucks of the honeycomb cat insides- so with a tune up and new cat , a magnaflow from ebay 57 + 30 installed and about 55 bucks for a tune up kit i was good to go

good luck
 
For the fan relay circuit, check your fuse and the relay.

For the misfires, (as Jeep-thing suggests) try some new plugs and also a cap and rotor, maybe some new plug wires as well. This is a good thing to do anyway, even if it doesn't correct the codes.
 
OK

So for the fan circuit:

1. Check the fuse and the relay;

For the misfiring cylinders:

1. Replace the spark plugs,

2. Replace the cap and rotor,

3. Replace the ignition wires,

Anything else? Please be patient, I am new to working on my own car.
 
You have a distributorless ignition - no plug wires, cap or rotor. take a look at your ignition rail (what plugs into the back of the spark plugs) when you take it off, clean out the ports with some electrical contact cleaner, and squirt some di-electric grease in there....or you could replace it if it looks like shit....but they are like $120 or so at a place like NAPA.
 
Whoops.... forgot that the 2000 has the coil rail. (my bad!). What JN said about the coil pack.
 
If it were me, I would disconnect the negative terminal on the battery, wait 30 minutes, reconnect it, and take it back for emissions testing, you may just pass when those codes are clear. Then change out spark plugs, flush and fill any fluid that does not look new, and be done.
 
Also check the injector wiring. My 2000 had melted some of the injector wires together at some point in its life. Someone went in and seperated them and twisted some of them together. I seperated, soldered the connections and covered the repairs with electrical grease and heat shrink tubing. I think there was a bulletin about better heat shields for this problem.
 
Also the inspection station mentioned check engine light not working. Does the light come on with the ignition on and engine not running? If all is working properly it will be on then go out after starting. If not check for burnt out or missing bulb. Sounds like an eBay fix, "Hey runs great and no engine lights!" Once working you'll know if the other fix or fixes address the problems.
 
Your check engine light may have been purposely disabled. Check and see if there is a bulb in it. The CEL comes on for a variety of reasons, many of which don't affect the running/driving at all. (A leaking gas cap will light the CEL! The dealership can diagnose this for $75.00) Some people get tired of looking at a lit/intemittent light on the dash and pull the bulb.

When you go to change the plugs, be careful. That coil pack/rail is one expensive part. careful with the mounting tabs and real careful with the connector if you decide to disconnect it.

Go back on e-bay and look for an owner's manual. It took about a month for one to show up after I bought my '00. Cost me 5 bucks.

How many miles? A lot of people just drive cars now without any preventative maint. Your intermittent miss may well be the original factory plugs.
 
Reader said:
OK

So for the fan circuit:

1. Check the fuse and the relay;

For the misfiring cylinders:

1. Replace the spark plugs,

2. Replace the cap and rotor,

3. Replace the ignition wires,

Anything else? Please be patient, I am new to working on my own car.
Click to expand...
Have the vehicle tuned up, check to see if the fan is working, and most importantly, Don't ever buy a used vehicle sight unseen!!! (P.S. put a bulb back in the ck engine light, the fact that it didn't come on when you 1st turned the key should tell you something)
 
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