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  #1  
Old December 3rd, 2019, 17:48
gage1414 gage1414 is offline
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CPS Trouble

Good Evening
I have a 1988 XJ with the 4.0 in it and an automatic trans. Ive had issues with it sputtering, dieing, crank with no start, rough idle, and bad fuel mileage. ive tested all the sensors and all checked out except the CPS. The resistance is good but the voltage test to get .5 volts is bad. I replaced the CPS with an aftermarket sensor and it ran great for a few hours then i started having the same issues. i then checked the CPS again and same result bad voltage. this has happened three times which leads me to believe the ECU may being going bad or is bad. I pulled the ECU and took it apart and found two locations that had burn marks on the circuit board. before doing so I also found 3.5 volts coming from both wires on the CPS plugin.
#1. My question is that is there supposed to be voltage on those two wires and if so how much?
#2. is it possible my ECU is bad and in return burning up the new CPS's i have been installing?

Thank you in advance
Post Script: im sure this has been covered but ive been searching the forum for about three hours and cant find the answers im looking for.
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  #2  
Old December 4th, 2019, 05:48
Fatlip671 Fatlip671 is offline
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Re: CPS Trouble

Oem works best. I had an Infiniti G35 that did the same thing. My 98 XJ also had similar issues and burnt a set of Napa distributor and crank sensors. I switched to OEM and it worked.
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Old December 4th, 2019, 13:33
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Sean778 Sean778 is offline
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Re: CPS Trouble

Is there a wreckers near you where you could try to grab an ECU from a similarly configured XJ? I know the Renix XJs are becoming increasingly rare in the yards here.
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Old December 6th, 2019, 06:27
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cruiser54 cruiser54 is offline
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Re: CPS Trouble

Doubtful CPS would cause ECU issue or vice-versa.

Ever gone to www.cruiser54.com and completed Tips 1 through 5?

Your CPS signal could be getting lost passing through the C101 connector....
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Old January 2nd, 2020, 17:19
gage1414 gage1414 is offline
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Re: CPS Trouble

I have most of those upgrades on the cruiser website including the grounds and the C101 connecter bypass. i waited for about two months and finally got a true MOPAR CPS and installed it today to the same effect. i drove the jeep for about two hours and the cps failed. started reading about 295 ohms. ive checked just about everything but cant understand why i keep blowing through CPS sensors. ive checked the ECU, grounds, battery voltage, temp of motor and the intake and exhaust mainfolds to see if there was a leak that was causing the sensor to heat up and fail. but i havnt found any reason.
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Old January 2nd, 2020, 19:51
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cruiser54 cruiser54 is offline
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Re: CPS Trouble

test the CPS output.
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