SigFig

I just ran a computer diagnostics on my 93' V6 4.0 Grand Cherokee Laredo. Feedback came is as followed:

Defiantly a clogged catalytic converter

then the worst...CPU problems

the oxygen and throttle position sensor isn't getting the right voltage and can be due to the CPU
the CPU is saying the desired idle is 8,000 rmps!!! when it should be 800 to 1,000...

so anyone had this problem? The car shifts hard, slow to accelerate, and revs up to fast.

They said take it to the dealership for a new cpu and reprogram. Can I just get a new cpu or reprogram my old one?

Bustedback

Can't reprogram a 93 ECM, you can only replace it or have it repaired. The O2 sensor creates its own voltage by a chemical reaction with the O2 in the exhaust gases, but they do have a heater circuit that requires voltage from the ECM to get the sensor up to temp faster. The TPS should have about .5 of a volt with the throttle closed and go to almost 5.0 volts at WOT. You may very well have a faulty ECM, that is usually the case when there are multipal strange codes and commands.

SigFig

So the computer is called ECU? And a 93' jeep ECU can't be reprogrammed, only replaced and then reprogrammed? I'm so tired of spending money, the local shop said the dealership has more in depth and sophisticated programs to run better diagnostics so I want to do that first, I'm not convinced changing the ECU and reprogramming will fix everything.

Bustedback

By repaired I mean it is tested and the faulty circuit is repaired. It could be any number of things inside the ECM (PCM, ECU, SBEC all the same thing), like a resistor, transistor, fried printed circuit board, or broken solder joints that can cause weird stuff to happen. Your local NAPA should know of soemplace that repairs them, but it might even cost the same if you can find a new or reman replacement. I would have the dealer or a Jeep specialist check it out first though.

SigFig

The dealership told me today they don't feel comfortable diagnosing a 93' and don't have the later equipment to do so....So I'm going blindly on what to fix or buy now....

GunsandMoney

This sort of thing pisses me off to no end. I had a similar experience today with the jeep dealer. All they do nowadays is plug in the stupid little code reader. If its not in there, they are clueless. WTF happened to all the good mechanics who actually had in depth knowledge of various parts on vehicles? They have all the backing and literature to properly narrow it down the the fault directly, but are too lazy or stupid to do so.

tiwvr1

clogged cat will cause many of the symptoms including 02 sensor code. check for input voltage to the tps, should be 5 volts. Dont go jumping to conclusions about the computer. And the actual code definitons would help also, or just the number.

Willys55

seeing how that is a 93, try the key trick...key on, then off, then on, then off then back on and read the check engine light flashes...let us know what you find

SigFig

I knew about the key trick, I wish things was that easy. I just get the regular 55 which means its a completion of of the scan. I then found out if you disconnect your battery, the the car deletes all the recorded codes. Unknowingly, I disconnected the battery a week ago because someone told me when you change alot of electrical things to reset the battery....so I got a problem with my car and no mechanic can diagnose it't.

I know I have a clogged cat converter and exhaust leak I'm getting that fix in a couple weeks

but the problems with the accelerating,shifting, and reeving up hard can't be set to a single thing. It can be narrowed to TPS, crankshift sensor, or the dreaded ECU.

I can't find the ECU though to read the code off it to get a price for it, I think I see it under the passenger side but I can see it enough to read a code.... One place set the price range for it though from 160-300 which is not bad due to most newer cars are 1000 and up

I'm search around auto shops for a Haynes Book car manual but I doubt I can get one for a 93

SigFig

The auto shop said I had low voltage on my 02 and TPS but he automatically said it can be directed to the ECU...he said the ECU is saying the desired idle is 8,000 which it doesn't ever do that when it cranks, the idle is like 800 to 1,000. I was willing to pay money for a real diagnosis from the dealership but they said they don't feel comfortable doing OBDI's that their equipment is 4 generations ahead of OBDI's