So I replaced the TPS on my 94 4.0 and accidentally left the ignition on for about 30 minutes and heard a loud clicking coming from the relay box by the battery. Now I have no CEL or buzzing when key turned on, no fuel pump and no spark can I assume the ECM was ruined.jumping across the fuel relay runs the fuel pump, swapping relays doesn’t work. Prior to the whole ignition debacle, the vehicle wouldn’t start if it was less than 35 deg F, above 35 fired right up ran like a champ so in trying to fix that I have replaced: Cm sensor, crank sensor ,TPS, dist cap and wires, O2 sensor, plugs, rotor, and both temp sending units.
Diagnosing ECM problems
- Thread starter Bear4
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I would highly suggest sending it to Mark at Wrangler Fix:
wranglerfix.com
He is beyond a doubt one of the most well known guys in the Jeep community and all he does day-in-and-day-out are PCM repairs and replacements. He is super easy to get ahold of and very fast turn around time. I can promise you that you'll never have better customer service than you'll get with Mark.
Anyways, that's my suggestion. He can test it for you and if it's faulty he'll take the cost of testing off the cost of a replacement PCM.
Jeep Wrangler Module Test - Wrangler Fix
If you suspect your PCM, ECM, ECU, or computer is bad in your Jeep Wrangler you can use this service to have us test it for you.
wranglerfix.com
He is beyond a doubt one of the most well known guys in the Jeep community and all he does day-in-and-day-out are PCM repairs and replacements. He is super easy to get ahold of and very fast turn around time. I can promise you that you'll never have better customer service than you'll get with Mark.
Anyways, that's my suggestion. He can test it for you and if it's faulty he'll take the cost of testing off the cost of a replacement PCM.
Thank you I have a spare you that can swap parts from and I am going to swap out the ecu and see if either one starts…soon as it warms up a little outside.I would highly suggest sending it to Mark at Wrangler Fix:
Jeep Wrangler Module Test - Wrangler Fix
If you suspect your PCM, ECM, ECU, or computer is bad in your Jeep Wrangler you can use this service to have us test it for you.
He is beyond a doubt one of the most well known guys in the Jeep community and all he does day-in-and-day-out are PCM repairs and replacements. He is super easy to get ahold of and very fast turn around time. I can promise you that you'll never have better customer service than you'll get with Mark.
Anyways, that's my suggestion. He can test it for you and if it's faulty he'll take the cost of testing off the cost of a replacement PCM.
when the battery goes below 10vdc, (fsm says 9.5) the ECu goes off line. 1994 YJ right. 4.0L right? a/t or m/t not told.
the cure is charger the battery , or jump start it or, buy a new battery.
cardone does them. top one in USA. (ordered from Napa, cardone is not direct sales)
the caps in any ECU this old can be bad. the endless story.
I call bad wiring, not ECU.
in PA.
the cure is charger the battery , or jump start it or, buy a new battery.
cardone does them. top one in USA. (ordered from Napa, cardone is not direct sales)
the caps in any ECU this old can be bad. the endless story.
you're in the salt belt, wires and connections fail, easy.
I call bad wiring, not ECU.
in PA.
this car the 1994, (91 to 95)
has the ASD relay
if spark is dead after 3 seconds cranking , and the ASD drops out. (de-energizes) that
means the PCM discovered the output pin ASD is overloaded.
I have posted here 10 times all things that cause that.
when ASD drops out all spark , fuel and fuel pump relay go off line. dead.
that is it whole purpose to end 'crash and burn' as seen on TV. and by law.
see ASD if: below.
I made this drawing just for ASD failures. top cause is 02 shorted, the heater shorts and bam, dead.
has the ASD relay
if spark is dead after 3 seconds cranking , and the ASD drops out. (de-energizes) that
means the PCM discovered the output pin ASD is overloaded.
I have posted here 10 times all things that cause that.
when ASD drops out all spark , fuel and fuel pump relay go off line. dead.
that is it whole purpose to end 'crash and burn' as seen on TV. and by law.
see ASD if: below.
I made this drawing just for ASD failures. top cause is 02 shorted, the heater shorts and bam, dead.
the voltmeter test, is the PROOF it did.
DTC error code 42 is ASD output was detected OVERLOADED
wire a142 is the wire bus that was overloaded.
the ASD relay must be closed full time cranking or running.
the ASD senses wire 57 , if the voltage is too low the PCM flags it < overloaded. my guess, about 9v.
so a weak car battery is never wise to have. the FSM tells you to keep it charged all the time while troubleshooting all electrics.
try running with 02 unplugged yet.
check out pin 7 FPR, if the pump shorts as they sure can do , it overloads ASD pin 22, and bam , ASD dROPS DEAD>
DTC error code 42 is ASD output was detected OVERLOADED
wire a142 is the wire bus that was overloaded.
the ASD relay must be closed full time cranking or running.
the ASD senses wire 57 , if the voltage is too low the PCM flags it < overloaded. my guess, about 9v.
so a weak car battery is never wise to have. the FSM tells you to keep it charged all the time while troubleshooting all electrics.
try running with 02 unplugged yet.
check out pin 7 FPR, if the pump shorts as they sure can do , it overloads ASD pin 22, and bam , ASD dROPS DEAD>
So I was able to swap ASD relays and ecu after fully charging the battery and I also installed a new cam CPS. swapping ecu it started right up and ran great. I believe the underlying problem was the CPS, reason being prior to the leaving the key on debacle it wouldn’t start when temp was below freezing. Nothing else but changing the CPS corrected that.