1999 Jeep Cherokee - Answered Questions & Fixed issues
P0420 2003 Jeep Grand Cherokee 4.0 6cyl
This code is a catalyst efficiency code. The catalytic converter is most likely the problem, but it could still be caused by a defective oxygen sensor. The easiest way I know to check for this code is with a scan tool that is capable of reading live data stream. You need to look at the upstream and downstream oxygen sensors, and see if they are mirroring each other. In other words, if the upstream (the one before the catalytic converter) is reading .700, and the downstream ( the one behind the catalytic converter) is reading .700, or anywhere near that, then you have a problem. The numbers are just examples. The upstream should constantly swith from high to low voltage. If the downstream is identical, or even remotely close to having the same reading as the upstream, then you most likely have a defective catalytic converter. This does correspond to what happened a couple of weeks back. A misfire will take out a catalytic converter if not repaired quickly. Also, if you had a converter that was marginal, and was close to failure, then that misfire may have been just what it needed to fail.
6/25/2021 11:06:42 AM •
1999 Jeep...
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Answered
on Jun 25, 2021
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846 views
99 jeep cherokee code P0123 TPS high voltage,replaced TPS same problem after 5 min driving.I also replaced CPS ran smoother but same code again for TPS.Now what can I do?
the 90's jeeps are susceptible to having grounding issues, disconnect the battery, follow your ground wire from the battery to the block, use a file and clean the connections, there is a ground strap from the rear right head bolt (drivers side firewall) to the chassis, clean that up on both sides, and there is a ground connection from the computer to the chassis, clean those all up, clear your codes and try again.
4/8/2019 4:25:41 PM •
1999 Jeep...
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Answered
on Apr 08, 2019
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1,038 views
Sounds like the engine is running loud
a loud engine can mean a lot of things, could be worn valves piston rings etc, I myself have round the clock engine and it was noisy, but i used a can of engine restorer, and noticed with in ten minutes the difference, its expensive but on an old warn engine it had done the trick. might even help yours, it does not really matter how meany oil changes you do an engine will wear a bit, if its pulling ok with no difference then its not a really serious problem, it could just be a blowing exhaust manifold or downpipe, or even a damaged air filter. check these parts look for cracks in the manifold as these when the engine gets hot will expand, even just a tinny crack can make a loud noise. check the the manifold seal to the engine is good, good way to test the seal is water in a squeezer bottle or spray, or even just look for blow marks on the engine. also check the engine oil cap, check it for a mayo looking oil color this can be a sign that the oil is getting damp or water is getting into the oil. this can also change the sound of the engine as the oil has become contaminated, oil can have a bit of water in there but its usually heated away with engine use. i hope this items help you find your problem.
2/1/2018 6:21:07 AM •
1999 Jeep...
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Answered
on Feb 01, 2018
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111 views
Air,heat does not blow out vents 99 jeep Cherokee.
this is real simple physics (simple tests find this) in order.
1: first engine must get hot,180f or more. (bad thermostat it cant)
2: that same water (coolant) must FLOW in the heater core.
the SM shows, in the HVAC chapter, checking the 2 core hoses
as they pass firewall to core by hand (skills) or IR gun
to see that they are near 150f or more,(water inside is hotter,dig)
if both are hot, flow may be good. bet yes.
leaving what. just one cause, the heat damper is stuck closed.
did you want to test or guess?
you never said. my guess is you want only guessing here.
in web bunny land.
so here i go., Mr. Carnac .
i guess, damper stuck, and then reading the SM
find out why.
3/16/2017 2:16:56 PM •
1999 Jeep...
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Answered
on Mar 16, 2017
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194 views
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