2002 GMC Jimmy engine light comes on and off

Tiny
JACKIE68
  • MEMBER
  • 2002 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 411,000 MILES
My daugther bought a Jimmy at an auction hoping to get a cheap winter beater. The engine light seems to go on and off at different times. She took it and had it scanned. It said it was a missfire in cylinder 1.
Changed the spark plugs, wires, router, still having the same problem.
When the engine light does come on the truck runs horrible, sounds bad, shakes. The shop that we took it to flushed the fluids and has gone to the point where they will no longer look at it cause they can't find out why the engine light comes on.
They told my daughter to take it to a dealership to have them look at it but she can't afford to put any more money into it.
Milage is horrible also. Could the cylinder itself be damaged somehow? Could it be a computer problem?
Thanks
Jackie
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Thursday, March 5th, 2009 AT 9:37 AM

46 Replies

Tiny
DAVE H
  • EXPERT
Could be a bad valve in the cylinder #1. Could be a bad injector for #1. Could be the computer. Does the code always come back as misfire on #1? It could be a wiring problem to the injector. Check the wire condition. Have cylinder #1 compression tested to rule out the valves. You could check for a bright blue spark on #1. But you say this is intermittent so you would need to do this when it is acting rough. If you get a good blue spark at this check then it's not a spark fault. Wiggle the injector wires to see if you can recreate the fault !
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Thursday, March 5th, 2009 AT 10:50 AM
Tiny
DAVE H
  • EXPERT
Hi Dave

Do you mind if I forward this to my daughter so that you can correspond with
her? She knows exactly what the guys said working on her truck and I am not
an automobile person at all.

Those seem to be great suggestions and I am sure Jess and her father can do
the things you mentioned. She can answer any of your questions better than I
can attempt.

Thanks

Jackie

Hey Jackie

Sure. Forward the email to your daughter and have her contact me.

Thanks
Dave H
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Thursday, March 5th, 2009 AT 11:56 AM
Tiny
JACKIE68
  • MEMBER
Hey Dave, its Jessica, Jackie's daughter. When the code comes back it is always a constant cylinder 1 misfire, they replaced the wires, plugs, alternator (cause it was going), did fuel injector flush, cleaned the fuel injectors said they were clean already, did a gas compression or something it registered at 56psi and the normal was 60 they said that wouldn't make a difference, replaced my fuel filter, replaced my rotator and distributer cap twice in case the first one I put in my self was faulty, and ya thats the jist of it. When the engine light comes on you can feel the engine limp and a gnawing/ grinding (like a metal on metal or belt of some sort rubbing) noise comeing from the drivers side on the engine ( only when accelerating). The engine limp/ misfire gets incredibly bad when I put anything less then 91 octane. Shes very picky. It use to seem that it only came on after using my 4X4 but it has done it before without me using my 4X4.
Any help at all would be greatly appreciated. Also when the light comes on it idles really low at around 500-600 rpm and on good days when the engine light is off and it sound smooth and great it idles at about 800-1000. When the engine it idleing really low it worries me like its gonna stall it self and the gauges for my enigne temp, oil temp and battery charge start to wiggle( sway back and forth only about 2mm but enough to make me start talking very VERY nice to my lovely truck)lol anyway any advice would be great
Thanks a bunch
Jess
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Thursday, March 5th, 2009 AT 6:09 PM
Tiny
DAVE H
  • EXPERT
Hey Jessica.

Sorry not replied sooner ... I cannot find any Technical specifications listed for a 2002 GMC Jimmy ... could you please supply your vehicles VIN# .. this should be located in the bottom right of windshield !! .. thanks .. in the meantime please remove and clean the MAF sensor ..


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Saturday, March 7th, 2009 AT 9:15 AM
Tiny
JACKIE68
  • MEMBER
Sorry, what is a MAF sensor?
Thanks for your help
will pm you with our daughter's vin
husband is looking in the repair manual to find out what a MAF sensor is and can't find it.
Thanks
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Saturday, March 7th, 2009 AT 9:30 AM
Tiny
DAVE H
  • EXPERT
Without the VIN# I can't supply any tech details or spec's or even know which sensors your vehicle has?. My manuals are not showing a GMC jimmy made in 2002? . The sensor could be a MAP sensor on your vehicle ! Let me know
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Saturday, March 7th, 2009 AT 9:53 AM
Tiny
DAVE H
  • EXPERT
These spec's are taken from a 2001 GMC jimmy .. they SHOULD be the same !!

Manifold Absolute Pressure (MAP) Sensor (2.2L VIN 5)On top center of engine.
Manifold Absolute Pressure (MAP) Sensor (4.3L VIN W)On top center of engine.
Mass Airflow (MAF) Sensor (4.3L VIN W)On air intake assembly


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Saturday, March 7th, 2009 AT 9:55 AM
Tiny
JACKIE68
  • MEMBER
Here is another thing.
My husband got an ECU(don't know if this is the proper name for it) from a auto wrecker when the truck had the engine light on. So he switched the ECU and when the truck key was turned the light didn't come on. Now we couldn't keep the new ECU in cause the anti theft wouldn't let us acually start the truck(we are presuming the anti theft would have to be reprogrammed to reconize the new ECU) do you know how to reprogram an anti theft or will a dealership do this for us?
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Saturday, March 7th, 2009 AT 10:19 AM
Tiny
JACKIE68
  • MEMBER
My husband is looking up those sensors in the book.
My daughter is on her way here with her truck.
I will pm you with the VIN when she gets here.
Thanks
Jackie
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Saturday, March 7th, 2009 AT 10:26 AM
Tiny
JACKIE68
  • MEMBER
I have my daughters VIN. Can you private message me cause it won't let me cause I don't have 10 replys or something like that.
I am uncomfortable about posting my daughters VIN
on the internet cause I don't know if anyone can do anything with it.
Thanks
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Saturday, March 7th, 2009 AT 10:58 AM
Tiny
DAVE H
  • EXPERT
Follow these procedures to the LETTER !!! ECU/BCM/VCM are the same thing !! just BCM is body control module

PROGRAMMING
PASSLOCK(tm) AUTO LEARN PROCEDURE
NOTE:This procedure allows relearning of BCM or VCM/PCM learned data code after replacement of BCM, sensor or VCM/PCM. DTC B3031 will set when entering programming mode.

Turn ignition off. Replace failed component. With transmission in Park (A/T) or Neutral (M/T), momentarily rotate ignition switch to START position (engine will not start), and then leave in RUN position. SECURITY indicator light will stay on for 10 minutes. After 10 minutes, when light turns off, turn ignition switch to OFF position for 5 seconds.
Repeat step 1 twice more. Auto learn procedure will be completed during next start attempt. If VCM/PCM was replaced, reprogram VCM/PCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

Using scan tool following scan tool manufacturer's instructions, check for DTCs. If Passlock(tm) DTCs exist, see SELF-DIAGNOSTIC SYSTEM . If engine performance-related DTCs exist, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. After repairs, check system operation. See ANTI-THEFT SYSTEM DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM.


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Saturday, March 7th, 2009 AT 11:26 AM
Tiny
DAVE H
  • EXPERT
I have sent you a PM ...is the vehicle a 4.3L engine ?


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Saturday, March 7th, 2009 AT 11:45 AM
Tiny
JACKIE68
  • MEMBER
It is a 4.3L
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Saturday, March 7th, 2009 AT 2:44 PM
Tiny
DAVE H
  • EXPERT
Sorry not got back to you this afternoon family stuff LOL .. How are we doing .. did you check the MAF sensor ? or did you try reprogamming the new ECM .. your vehicle is 2001 model L35 engine ... let know how you are doing ?


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Saturday, March 7th, 2009 AT 6:41 PM
Tiny
JACKIE68
  • MEMBER
Her truck is a 2002, 4.3litre
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Sunday, March 8th, 2009 AT 2:13 PM
Tiny
DAVE H
  • EXPERT
I know .. it was sold in 2002 .. was actually made in 2001 .. how are things progressing !!


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Sunday, March 8th, 2009 AT 2:26 PM
Tiny
JACKIE68
  • MEMBER
Her ownership says it is a 2002
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Sunday, March 8th, 2009 AT 7:03 PM
Tiny
DAVE H
  • EXPERT
OK the car is a 2002 ... they do not make vehicles one day and sell them the next ...it may have been registered and sold in 2002 but it was actually manufactured in 2001 ..GMC did not make a JIMMY after 2001 ..I'm sorry if this upset's you .. but it does not detract any value from the car ... it is a 2002 registered vehicle ... but from my point of view it is a 2001 model every tech you meet while you have the vehicle will tell you they did not make a jimmy in 2002 ... aside from this issue have you made any progress on the repair of the vehicle ??


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Sunday, March 8th, 2009 AT 7:36 PM
Tiny
JACKIE68
  • MEMBER
We changed out the PCM and the truck's engine light still comes on and still acts like it did prior to the new PCM.
We were told that it is most likely the distibutor. Sorry, not sure if I am saying this all right.(Not into cars but can type, somewhat : ))
We were told that there is some kind of filter in there that can clog up enough to make the missfire happen. We are going to try to blow it clear or if that fails replace it. My husband was told that this guy is 100% sure that is what the problem is. We will let you know how it goes.
Thanks
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Friday, March 13th, 2009 AT 5:45 PM
Tiny
DAVE H
  • EXPERT
Remove and clean the CKP (crankshaft position sensor)

High Voltage Switch Ignition System
Used on the 4.3L, 5.0L and 5.7L engines, the High Voltage Switch (HVS) ignition system consists of the PCM, distributor, ignition coil driver module, ignition coil and Camshaft Position (CMP) sensor. Ignition control and by-pass functions are controlled by the VCM.
Camshaft Position (CMP) Sensor

CMP sensor is similar to CKP sensor. CMP sensor provides one pulse (1X signal) per camshaft revolution. PCM uses this signal in conjunction with the crankshaft position to determine which cylinder(s) are misfiring.
Crankshaft Position (CKP) Sensor

CKP sensor is located in the front engine cover. Air gap between sensor and target wheel is preset and is not adjustable. Target wheel has 3 or 4 slots, depending on weather the engine has 6 or 8 cylinders and is keyed to the crankshaft. Rotation of target wheel creates a change in the magnetic field of the sensor which results in an induced voltage pulse. Based on these pulses, PCM is able to determine crankshaft position and engine speed. PCM will then activate the fuel injector and provide spark to distributor.
Distributor

Distributor assembly contains the Camshaft Position (CMP) sensor, cap, rotor and shaft. A Diagnostic Trouble Code (DTC) will set when distributor is installed a tooth off in relation to the camshaft. Distributor is not serviceable.
Ignition Control Module

ICM receives ignition control signals from the PCM which in turn triggers the ignition coil. Since the PCM controls spark timing and ignition control during crank and run cycles, there is no by-pass mode. ICM is not serviceable.


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Friday, March 13th, 2009 AT 6:02 PM

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