Dear fellowship of jeeps.
I have bought this XJ 2000 but it’s not running well. Lack of power, slight engine vibration, rough idle. I have changed ignition coil, injectors, spark plugs, all sensors that I can think off to to avail.
I then bought an scanner to have closer look of what’s going on. Specifically fuel trim and so on.
Im new to this scanning thing. I’m getting this read out and can’t get my head around it.
What du you guys gets from these readouts….is my PCM sick




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You have a OBDII and ABS scanner not a computer scanner. Unless I woke up on a different planet, your scanner is capable of reading codes produced by your vehicles computer and clearing them. It doesn't report on fuel trim levels, O2 readings and such because it is not capable therefore displays "N/A". It takes a expensive scanner to read the computers output. Now if your O2 sensor failed, it would give you a code that would tell you whether it was upstream or downstream of the cat.

A P0601 code "stands for “Internal Control Module Memory Checksum Error.” It is triggered when the powertrain control module (PCM) detects an internal problem, typically a failed Memory checksum test. The PCM's memory checksum test is performed regularly." would indicate a PCM problem.

As far as your problems XJ problems go, I would first do a compression check. The problems you brought up could be a problem with the compression in one cylinder. Rule that out first.

 

Alright ! Got it, What I have is just a code reader , no live data an so on, damn. Anyway thanks for the reply Im already deep inside this XJ rabbit hole and can't get out.

Im off to RockAuto/Amazone for compression test equipment

 

What model scanner is it?

Your screen appears to be the readiness monitors. If you just cleared any codes, The readiness monitors should show INC (incomplete) until the system learns again and has completed the proper drive cycle. Not all vehicles support every monitor so those show as N/A.

It appears your model is this one:

https://www.otctools.com/products/OBD-II-and-ABS

It does say Live Data so perhaps you should read the manual.

 

That’s exactly what I’m talking about. I bought this scanner for live data monitoring, etc fuel trim. That why I find it suspicious that it’s read N/A for every single sensor..and thinking the PCM might have a malfunction. The Jeep also uses crazy amounts of fuel, ( I know Xj uses a lot of fuel)

It’s run like sh… and uses tons of fuel…

 

That code reader should read codes for a 2000, and you would need to check the user manual as to whether, how it reads live data

many, like my $30 BAFX, communicate with a phone APP, (Torque Lite is free)

main O2 sensor would be the first thing I checked on it, if they play up, your truck will run like crap and use a **** ton of fuel

They can be tested for functionality using tests in the FSM, but I believe simply disconnecting it is a good test to see if it is causing the problem

How many miles per gallon do you get ?

Definitely reset your PCM, by disconnecting battery, short main cable to ground. I would also check and clean the main PCM ground connections

 

Also make sure the dash shows it's warming up, otherwise it'll suck fuel thinking it's cold.

 

A Friend is coming over with a PCM to swap, we will then see if it makes any difference, in the mean time I’ll go after all the grounds with some sandpaper.

it’s a 2000 with 145000 miles and rounds 6-7 mpg

 

Disconnect your o2 sensor connectors or find the heater relays and pull them out.that will invalidate the o2 sensors and push to a pre programmed mode. Not perfect butstill very effective. Also if your coolant temp shows below halfway to 210 you will gobble gas...you are dumping gas into that engine...your plugs are probably black

 

I doubt the PCM will make a difference as they very rarely go bad. When the do, it's usually a blown injector driver and one injector isn't firing. In that case, you need to fix the source of the problem (shorted wire, bad injector, etc) before you try a new PCM or you'll just kill that one too.

 

I would also step back before fitting another PCM

You have not made it clear, but does your code reader not connect and scan codes ? Did you get any codes ?

You need to investigate this FIRST, before fitting another PCM (in my opinion)

an el-cheapo code reader that works to your phone is cheap as chips, mine is plugged in all the time

at least pull the main O2 plug and see if it idles better before fitting a PCM

6-7 mpg is very bad, should get about 3 times that

 

The manual -> https://otctools.com/sites/default/f...fr-es_revc.pdf
Looks like your under the I/M screen instead of "View Data".

 

Thanks, you guys were Right , I swapped a friends PCM and it didn’t improve anything. Another scanner indicated misfire on cyl no One. I’ll open the harnes and check Al the wires. Thereafter a compressor check,