Mechanics

CHEVY SERVICE ENGINE SOON LIGHT ON P0300

2002 Chevrolet Silverado

Engine Performance problem
2002 Chevy Silverado V8 Four Wheel Drive Automatic 54,000 miles

I looked through the Repair Question Forums and do not see anything specific that helps answer what might be wrong with my vehicle so now I am sending my question to you and very much hope that you may be able to help. I have a 2002 Chevy Silverado Pick-up Truck. V8, 6.0 liter engine, K2500. 4 Wheel Drive. Automatic. 54,000 miles. Check Engine Soon light is blinking. Code P0300 Random misfire. Light does not come on at all while driving around town. Only comes on when on the highway at over 60 mph. The light blinks for several minutes and then eventually goes out. Then several minutes later it comes back on blinking again. When the light comes on, the truck continues to run smoothly and there is no indication that something is wrong.

I brought the truck to be serviced. They replaced Intake manifold gasket with new design. (They said there is a bulletin out from GM that if the gasket is the color green then it could become defective. They said my truck had the green one.) The garage seemed to assume that because of this bulletin that this must be what was wrong. They also did an oil and filter change and changed all eight Spark Plugs. ( My truck had 100,000 mile spark plugs so I’m not sure why they needed to change the spark plugs now).

The next day, I went on the highway with the truck and once again the light was blinking. I called the garage and they said to bring it back and they would check every thing again. At this time they rechecked the connections to intake and cleaned engine grounds and also replaced the fuel filter. When I picked up the truck, they said everything should be fine now. I took it on the highway and again the light was still blinking. I called the garage again and they said to bring it back. When I picked up the truck they said they once again checked everything and it now definitely should be fine. I went on the highway and the light is blinking on again.

I’m very frustrated and aggravated. It cost me almost $540.00 and I am feeling that bringing my truck to this garage might have been a waste of time and money because they did not solve the engine light problem. I’m thinking that they are not following diagnostics thoroughly to solve the problem. The second time I brought the truck back, I felt like I was being brushed off. They don’t seem to be doing anything more about it. I don’t know what to do next.

Also, prior to having this service engine light problem, I had this vehicle at the dealer and was told the Engine Oil Cooler Lines are starting to leak. They said they would need to replace the hose. The garage that I brought the truck to for the engine light said that this would not affect the light coming on and it is a separate problem. True?

One other thing I can think of mentioning: When I first start driving the vehicle I can hear a engine tapping type of noise but again I think this might be a separate problem. (I told the garage this as well.)

I am hoping you could give me some insight on what might be wrong. I would really appreciate any suggestions. I’m really discouraged! Please help!
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Macfin
March 19, 2009.



This is most likly the cause, and the fix is free: This is a TSB also from Chevy:
Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0420 or P0430 TECHNICAL SERVICE BULLETIN Reference Number(s): 06-06-04-046,  Date of Issue:   September 12, 2006 Related Ref Number(s): 06-06-04-046 ARTICLE BEGINNING SERVICE INFORMATION If you encounter vehicles that exhibit the above conditions, refer to SI for the appropriate DTC(s) set. If no trouble is found, the cause may be due to an ECM ground terminal that has corroded with rust over time. Inspect the main engine wiring harness ground terminal (G103) for this condition. The wire terminal (G103) attaches either to the front or to the rear of the right side cylinder head, depending on the model year of the Full Size Pickup and/or Utility Trucks. If the ECM ground terminal has been found to be corroded, then follow the service procedure outlined in this bulletin to correct the corrosion issue. Fig. 1: Engine Wiring Harness Ground Terminal Location (2007 Full-Size Pickup and/or Utility Trucks) Courtesy of GENERAL MOTORS CORP. Fig. 2: Engine Wiring Harness Ground Terminal Location (1999-2006 Full Size Pickup and/or Utility Trucks) Courtesy of GENERAL MOTORS CORP. 1. Remove either the nut or bolt securing the main engine wiring harness ground terminal (G103) to the right cylinder head. Refer to the above illustration to determine where the ground is located on the vehicle (1). 2. Remove all rust from the ground terminal, the cylinder head and the retaining nut or bolt. 3. Position the main engine wiring harness ground terminal and install the nut or bolt. Tighten:: Tighten the retaining nut or bolt to 16 N.m (12 lb ft). 4. Apply some type of electrical moisture sealant to protect the harness terminal from further corrosion. Affected Model(s): 1999-2007 Cadillac, Chevrolet, GMC Full-Size Pickup and/or Utility Trucks; with 4.8L, 5.3L, 5.7L, 6.0L or 6.2L VORTEC GEN III, GEN IV, V-8 Engine (VINs V, C, T, Z, B, 3, M, 0, J, R, U, N, Y, K, 8 - RPOs LR4, LY2, LM7, L59, L33, LC9, LH6, LMG, LY5, L31, LQ4, LQ9, L76, LY6, L92); with Active Fuel Management(tm) and E85 Flex Fuel Page 1 of 1 Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P030... 3/19/2009 src="http://www.2carpros.com/forum/automotive_pictures/62217_K2500_1.jpg" alt="http://www.2carpros.com/forum/automotive_pictures/62217_K2500_1.jpg" />


Merlin2021
Mar 19, 2009.
Hello merlin2021,
Thank you so much for your very prompt response. I really appreciate it. The garage had said that they cleaned engine grounds but I will double check the EMC ground terminal and will remove all rust if found. Hopefully, this is the problem. I will let you know if it worked.

Thanks so much!
Macfin

Tiny
Macfin
Mar 20, 2009.
Dont forget to scuff up the head surface! You want these nice and brite, I use emory cloth, get it at home depot in plumbing dept. Comes on a roll about an inch wide.

Merlin2021
Mar 20, 2009.
Did this fix the problem Mackn?

Tiny
Storyteller
Dec 15, 2009.
His last post was March 20, so it probably did.

Merlin2021
Dec 15, 2009.
. The only problem is that I don't see the ground bolt/nut in proximity to the oil fill tube/right front-side of cylinder head.

I see what looks like a threaded hole where maybe a threaded stud could go into. But I don't even see a loose wire that should go to it.A bit perplexed.

It has 70K miles, randomnly misfires above say 60 mph and reflects code P0300.

Any help would be OUTSTANDING!

Thanks so much!

Tiny
Storyteller
Dec 16, 2009.
Does not always attach at the front, check the rear of the head too!

Merlin2021
Dec 17, 2009.
I have a misfire problem with my 98 k1500. There is a similar looking mesh type ground that hooks up to the back of the head. When tightening the nut I didnt have much room, consequently I stripped the nut then pounded half of a washer in there to tighten the ground. I am not positive that it is a good ground. Is it plausible to cut the wire and tack it to a different part of the truck?

Tiny
Evantyrrell
Mar 5, 2010.
The wire terminal (G103) attaches either to the front or to the rear of the right side cylinder head, depending on the model year of the Full Size Pickup and/or Utility
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Merlin2021
Mar 5, 2010.

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