2002 GMC Jimmy engine light comes on and off

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 !!

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

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

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 ..

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

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

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

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?

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

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

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.

I have sent you a PM ...is the vehicle a 4.3L engine ?

It is a 4.3L

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 ?

Her truck is a 2002, 4.3litre

I know .. it was sold in 2002 .. was actually made in 2001 .. how are things progressing !!

Her ownership says it is a 2002

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 ??

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

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.

Thanks for the info
I will pass this on to Jess and my husband cause you lost me after the first sentence : ))
Jackie

Hi Dave, Thanks so much but we are still in the dark with the engine warning light on. My husband is reviewing your info right now. Yesterday he bought a new distributor(the whole unit) They don't rebuild them so he bought a new one. It came with a new cap and wires. He installed it and it is still misfiring. Seems only after the first start up. At first start up she(the truck) runs normal, no engine light comes on and it runs great. If a second or subsequent start up for the day is attempted then the engine light comes on and the truck runs horrible. We have also bought a CanOBD2 diqgnostic tool. Here is what it reads

P0300 Multiple Cylinder Misfire Detected

Stored Codes
P0405 EGR Position Sensor Circuit Low Input
P0418 Secondary Air Injection System Relay A Control Circuit

Pending Codes

P0300 Multiple Cylinder Misfire Detected
P0141 HO2S-12 (Bank 1 Sensor 2) Heater Circuit Malfunction
P0155 HO2S-21 (Bank 2 Sensor 1) Heater Circuit Malfunction
P0135 HO2S-11 (Bank 1 Sensor 1) Heater Circuit Malfunction
P0405 EGR Position Sensor Circuit Low Input
P0418 Secondary Air Injection System Relay A Control Circuit

Diagnostic Information

Parameter Description Value
DTC for which Freeze Frame was Stored P0300
Fuel System 1 Status Closed Loop - fault with at least one oxygen sensor
Fuel System 2 Status Closed Loop
Calculated LOAD Value 3.53 %
Engine Coolant Temp 183.20 °F
Short Term Fuel Trim - Bank 1 -7.81 %
Long Term Fuel Trim - Bank 1 -2.34 %
Short Term Fuel Trim - Bank 2 -7.03 %
Long Term Fuel Trim - Bank 2 -3.13 %
Intake Manifold Absolute Pressure 13.03 inHg
Engine RPM 618.50 rpm
Vehicle Speed Sensor 0.00 mph
Air Flow Rate Mass Air Flow Sensor 0.87 lb/min
Absolute Throttle Position 1.96 %
Click here to view Monitor Status

Monitor Name Monitor Icon Status
MIL ON
Misfire Monitoring
Complete
Fuel System Monitoring
Complete
Comprehensive Component Monitoring
Complete
Catalyst Monitoring
Not Complete
Heated Catalyst Monitoring
Not Supported
Evaporative System Monitoring
Not Complete
Secondary Air System Monitoring
Not Complete
A/C System Refrigerant Monitoring
Not Supported
Oxygen Sensor Monitoring
Not Complete
Oxygen Sensor Heater Monitoring
Not Complete
EGR System Monitoring
Complete

I am not sure if this will help you or not but thought it might.
Once again thanks for helping
Sorry for taking up your time

Hey Jess. You are not taking up my time .. this is what we are here for ..no need to be sorry .. OK I really need you to clean the CKP .. if this is dirty or bad it will cause multi misfires ? it should set it's own code but not alway's ?? let me know and i will review your data in the meantime

My husband has went outside to clean the CKP sensor
thanks

My husband can't find the CKP sensor. Can you send a link to a pic of where it is or maybe describe where it is or located near?
thanks
Jackie

Sorry I had to pop out ..it is just near/behind the crankshaft pulley that has the alternator belt on etc. CKP sensor is located in the front engine cover. Crankshaft Position (CKP) Sensor (4.3L VIN W).....On front of engine, near crankshaft pulley.

My husband found it a couple of hours ago, I have been having computer problems so couldn't check email until now.
He cleaned the sensor(was very dirty, coated with oil and debris) When truck was restarted the engine light blinked for about 5 seconds then stayed on.

OK ..but is it running bad still ?? or better .. or exactly the same as before (misfiring) coughing chugging etc. ?? the light could be on because we have'nt cleared the codes !!!

it is still running the same
Idling went from 750 to 600 to 550 while in park

my husband said right about clearing the codes
He has had the battery disconnected for about 3 hours now

OK .. I need you to delete the fault codes with your scanner and restart the vehicle .. once running if it runs ok ..let it tick over for a minute or so .. rev it up a couple of times .. then turn it off and restart again and let me know how it runs once refired up and what codes return ?? Thanks

ok, husband is going out to do that right now.
thanks

my husband reconnected the battery, cleared the codes,started it, ran good for a minute then it started to run bad again. Then shut it off again waited a minute or two then restarted it. Engine light was not on the first time but was back on the second time.
He has the new diagnostic codes and I have to hook the tool to the computer and copy those for you.
Give me a couple of minutes
Thanks
Jackie

This is what the diagnostic tool is now saying
Do you think we should run it longer??


DTC Information
Stored Codes
P0405 EGR Position Sensor Circuit Low Input

Pending Codes
P0405 EGR Position Sensor Circuit Low Input

P0418 Secondary Air Injection System Relay A Control Circuit

Diagnostic Information
Freeze Frame Information
Parameter Description Value
DTC for which Freeze Frame was Stored P0405
Fuel System 1 Status Open Loop
Fuel System 2 Status Open Loop
Calculated LOAD Value 6.27 %
Engine Coolant Temp 132.80 °F
Short Term Fuel Trim - Bank 1 0.00 %
Long Term Fuel Trim - Bank 1 -1.56 %
Short Term Fuel Trim - Bank 2 0.00 %
Long Term Fuel Trim - Bank 2 -1.56 %
Intake Manifold Absolute Pressure 13.32 inHg
Engine RPM 882.75 rpm
Vehicle Speed Sensor 0.00 mph
Air Flow Rate Mass Air Flow Sensor 1.40 lb/min
Absolute Throttle Position 0.00 %
Monitor Information
Monitor Name Monitor Icon Status
MIL ON
Misfire Monitoring
Complete
Fuel System Monitoring
Complete
Comprehensive Component Monitoring
Complete
Catalyst Monitoring
Not complete
Heated Catalyst Monitoring
Not Supported
Evaporative System Monitoring
Not complete
Secondary Air System Monitoring
Not complete
A/C System Refrigerant Monitoring
Not Supported
Oxygen Sensor Monitoring
Not complete
Oxygen Sensor Heater Monitoring
Not complete
EGR System Monitoring
Complete

my husband thinks that it is going to read a misfire again if left to run longer.
He thinks the hoses need to be checked cause he thinks there is a leak going to the EGR
What are your thoughts
He thinks once the EGR is fixed the other things will fall in line.

OK .. now diconnect the battery for 5 minutes.. at least ...reconnect battery ... this should delete ALL codes and KAM (keep alive memory) so have your radio code handy !.. check with scanner before restarting .... start her up and let her sit idleing for 5 mins minutes .. stop her .. restart her and let her sit for 5 minutes again .. if you think she will drive OK run her around for 5 minutes the second time and see how she behaves the results I need are :- 1) how did she run for the first 5 mins ..ie. good for 3mins bad for 2 .. etc. idleing up and down ? 2) how did she run for the 2nd 5 mins good/bad idleing up and down just chugging away etc. 3) what are the new codes .. Thanks

He sounds good to me .. check the hose .. I think we may have cleared up the misfire mystery .. although the egr will eventually cause a misfire as well ..

He is going out right now to do what you mentioned
I am not sure what time it is for you or where you are located but it is 9:35pm here, he is working in the cold and dark but we will see what happens here now and let you know.
We will then continue in the morning if this doesn't work.
Thanks very much for helping and I am sure we will find the problem some time, we better, or I guess you may see it listed on ebay.
The heading would be:
Real tool of a vehicle for sale!!!!!!
Ha! Ha!

first start up, minute one, engine running smooth, rpm 900
minute two, engine starts to develop shake, rpm 750
minute three, engine developing more shake, engine knocking, smell of gasoline in exhaust, rpm 550
and it just gets worse after that.
he is going to go back out to restart and run it for a second time

Ha ..Ha.. I wiil be watcing out for it ! ... NO ..we will get to the bottom of this ... can i first say that just because the fault code shows a bad EGR doesn't mean that the EGR is BAD .. all sensors are related to each other.. cousin's in a way.. lol ... so it still could be something else is throwing the EGR through a loop ..check the pipe .. and also wiggle the wires to see if this makes any difference .. also did we ever clean the MAF sensor ? .. this could show up as a fault on the EGR system ... it is also 9-45pm here now .. but i am inside ..lol .. I will be here around 11 am in the morning .. so we can cary on then with more daylight .. let me know