Got it back from Dealer. They were able to replicate the problem. They were not able to find anything else wrong so be default are taking a guess that its the PCM because if the irratic behavior. 100% covered under the 8/80,000 mile emisions warranty. They would say that this will fix it though since there is nothing blatantly indicating the PCM is malfunctioning. So they let me take it home and I am going to test it while it's cold over the weekend. Keeping my fingers crossed.
05 tahoe, loose all power for a split second
- Thread starter mkatts
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Rivieraracing
Full Access Member
So they replaced the PCM?
Sorry, yes they replaced the PCM.
It was a not the problem either though.:cryin:
I took it out today and the problem is still there. The good news is though that the error was a lot more dramatic. It cutout, I let off the throttle and it recovered. I stepped on the gas and it cut out again, but I kept my foot on the pedal at the same position to sort of play around with it. I found that it's not actually stalling, it's dropping back to idle. I know this because the tach would drop back to 1000 rpm's. Then when I let off and pushed back down on the gass it would start to speed up again until I got to about 60 then it would cut out again. So I started limping to the next exit to get home. I was able to maintain about 50MPH. Then tried to speed up and again. SES light came on and stayed on, got a message that the traction control system is disabled, then another message on the DIC that said "reduced engine power".
Pulled off to the side of the highway and called onstar. They read the PCM and said there is an error in the Throttle control system. Finally got a dang error code!
C0240So now, I have somewhere to look. They offered a tow, since it was till running I just said I would limp it back home. Well It would not go above idle and it was missing bad like I had 2-3 spark plugs disconnected. Wife suggested shutting it down and letting it sit for a minute. That worked. It stated right back up and I was able to drive normally back to my house. I got back home and called Autojoke and advanced. Neither had a listing for the throttle control server on the throttle body. I didn't know what it's proper name was. Nor did they have a lsiting for the pedal position sensor. Again not sure of it's proper name. Just what I called them. I got under the hood and pulled the plastic shroud off the top of the engine. It looks like the throttle servor is all one peice with the throttle body since it's riveted onto the throttle body. That part will not be warranty so I am a bit nervous of what it will cost. It could also be the pedal postion sensor though since both could explain that the problem clears once warm. Oh well thrid times a charm I hope!
It was a not the problem either though.:cryin:
I took it out today and the problem is still there. The good news is though that the error was a lot more dramatic. It cutout, I let off the throttle and it recovered. I stepped on the gas and it cut out again, but I kept my foot on the pedal at the same position to sort of play around with it. I found that it's not actually stalling, it's dropping back to idle. I know this because the tach would drop back to 1000 rpm's. Then when I let off and pushed back down on the gass it would start to speed up again until I got to about 60 then it would cut out again. So I started limping to the next exit to get home. I was able to maintain about 50MPH. Then tried to speed up and again. SES light came on and stayed on, got a message that the traction control system is disabled, then another message on the DIC that said "reduced engine power".
Pulled off to the side of the highway and called onstar. They read the PCM and said there is an error in the Throttle control system. Finally got a dang error code!
C0240So now, I have somewhere to look. They offered a tow, since it was till running I just said I would limp it back home. Well It would not go above idle and it was missing bad like I had 2-3 spark plugs disconnected. Wife suggested shutting it down and letting it sit for a minute. That worked. It stated right back up and I was able to drive normally back to my house. I got back home and called Autojoke and advanced. Neither had a listing for the throttle control server on the throttle body. I didn't know what it's proper name was. Nor did they have a lsiting for the pedal position sensor. Again not sure of it's proper name. Just what I called them. I got under the hood and pulled the plastic shroud off the top of the engine. It looks like the throttle servor is all one peice with the throttle body since it's riveted onto the throttle body. That part will not be warranty so I am a bit nervous of what it will cost. It could also be the pedal postion sensor though since both could explain that the problem clears once warm. Oh well thrid times a charm I hope!
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Took it back to the dealer today. They said the code means the communication between the accelorator module and the PCM was lost. They swapped out the accelorator module with a known good one. I took the trunk home to test it out for a couple days. If this is it, a new acel module is $550 installed!:wow:
We'll see...
We'll see...
Rivieraracing
Full Access Member
That's cool that they installed that part for you to test out, so you are saying that if that solves the problem then you have to pay? That's alot of coin but it would be cool if that did solve your problem! Keep us informed!!
If it fixes it, I will take it back and they will install a new module. This one is a "tester" know good module they keep on hand since they don't have a real way to test the module other than to replace it. They recognize that $550 is a lot of money to shell out to not fix a problem. I thought of looking for the part myself and installing it, but by having them do it, I get a 12 month/12000 mile parts/labor warranty on the repair, so I am going to let them do it. It's hard to have someone else working on my truck. I hate even getting new tires done. I have to stand out there and watch the whole time. Don't like others putting wrenches on my vehicles. But since I would have been guessing at the problem it would have cost me way more. I was prepared to buy the throttle body assembly because I thought the problem was the throttle server on it and it's rivetted onto the throttle body. If the accelerator module is $550, I don't want to think about what the throttle body assembly costs!
Rivieraracing
Full Access Member
I totally understand and feel that you are making a great decision, can't beat a 1 year warranty on a spendy fix. What happens if down the road the problem comes back after you spent the cash, will that money go towards the new fix?
ok heres your problem on the rear of cylinder head 2 this is the passenger side there is a ground that breaks partially. this grounds multiple circuits including the tac module ipc etc.trace it back and pull on it lightly if it pops apart there is your problem. theres a bulletin on this i will try to post but it's pretty long. hope this helps oh and by the way the dealer you are dealing with sounds like a bunch of idiots. did they even run bulletins?
xTooltipElement Service Information 2003 GMC Truck Yukon Denali | Avalanche, Escalade, Suburban, Tahoe, Yukon (VIN C/K) Service Manual | Document ID: 1869994
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#PIP3089B: SES Light And Reduced Engine Power DTC P0120 P0220 P1516 P2135 - keywords accelerator actuator APP blade body connector connection DTC L33 L59 LH6 LR4 LM7 LS1 LS2 LQ4 LQ9 module position reduce sensor - (Oct 31, 2006)
Subject: SES Light and Reduced Engine Power DTC P0120 P0220 P1516 P2135
Models: 2004-2006 Buick Rainer
2005-2006 Cadillac CTS-V
2003-2006 Cadillac Escalade
2003-2006 Chevrolet Avalanche, Corvette, Express, Monte Carlo, Silverado, SSR, Suburban, Tahoe, Trailblazer
2003-2006 GMC Envoy, Savana, Sierra, Yukon
2003-2006 Hummer H2
2005-2006 Pontiac GTO
Equipped with a 4.8 5.3 6.0 or 7.0 V-8 Engine
--------------------------------------------------------------------------------
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
A vehicle may be brought into the dealer for a reduced power message, and DTCs P0120, P0220, P1516, P2101, or P2135.
The Throttle Actuator Control (TAC) / throttle body type trouble codes, may be caused by a loose wiring crimp at the throttle body connector, or a broken throttle body circuit.
Recommendation/Instructions:
Complete the current SI diagnostics for any symptoms or trouble codes found. If a intermittent T/P or TAC module type code is occurring complete the inspections below.
Inspect all related throttle body terminals for a loose wiring crimp. The loose crimp may be difficult to find, and the poor connection will be between the terminal and the copper strands of the wire. Wiggle test the individual throttle body circuits to see if the concern can be duplicated.
Inspect the related circuits for broken wires inside the insulation. The outer wire insulation may look fine, but the internal copper strands may be partially broken. Breaks in the wires usually occur within 1 to 4 inches of the throttle body connector. Wiggle testing may also induce a trouble code to set.
On C/K trucks complete SI procedures for voltage drop on grounds G103 and G104. Grounds G103 or G104 may be loose or corroded.
If a terminal crimp or a broken wire has been found, repair or replace only the circuits involved. There is a throttle body pigtail connector available through GMSPO, but installing this pigtail connector may cause other intermittent TAC module/TP codes at a later date. If this pigtail must be used, please follow the SI procedures for Splicing Copper Wire Using Splice Sleeves. (the proper Kent-Moore crimping tool must be used for this repair)
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
© 2008 General Motors Corporation. All rights reserved.
--------------------------------------------------------------------------------
#PIP3089B: SES Light And Reduced Engine Power DTC P0120 P0220 P1516 P2135 - keywords accelerator actuator APP blade body connector connection DTC L33 L59 LH6 LR4 LM7 LS1 LS2 LQ4 LQ9 module position reduce sensor - (Oct 31, 2006)
Subject: SES Light and Reduced Engine Power DTC P0120 P0220 P1516 P2135
Models: 2004-2006 Buick Rainer
2005-2006 Cadillac CTS-V
2003-2006 Cadillac Escalade
2003-2006 Chevrolet Avalanche, Corvette, Express, Monte Carlo, Silverado, SSR, Suburban, Tahoe, Trailblazer
2003-2006 GMC Envoy, Savana, Sierra, Yukon
2003-2006 Hummer H2
2005-2006 Pontiac GTO
Equipped with a 4.8 5.3 6.0 or 7.0 V-8 Engine
--------------------------------------------------------------------------------
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
A vehicle may be brought into the dealer for a reduced power message, and DTCs P0120, P0220, P1516, P2101, or P2135.
The Throttle Actuator Control (TAC) / throttle body type trouble codes, may be caused by a loose wiring crimp at the throttle body connector, or a broken throttle body circuit.
Recommendation/Instructions:
Complete the current SI diagnostics for any symptoms or trouble codes found. If a intermittent T/P or TAC module type code is occurring complete the inspections below.
Inspect all related throttle body terminals for a loose wiring crimp. The loose crimp may be difficult to find, and the poor connection will be between the terminal and the copper strands of the wire. Wiggle test the individual throttle body circuits to see if the concern can be duplicated.
Inspect the related circuits for broken wires inside the insulation. The outer wire insulation may look fine, but the internal copper strands may be partially broken. Breaks in the wires usually occur within 1 to 4 inches of the throttle body connector. Wiggle testing may also induce a trouble code to set.
On C/K trucks complete SI procedures for voltage drop on grounds G103 and G104. Grounds G103 or G104 may be loose or corroded.
If a terminal crimp or a broken wire has been found, repair or replace only the circuits involved. There is a throttle body pigtail connector available through GMSPO, but installing this pigtail connector may cause other intermittent TAC module/TP codes at a later date. If this pigtail must be used, please follow the SI procedures for Splicing Copper Wire Using Splice Sleeves. (the proper Kent-Moore crimping tool must be used for this repair)
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
© 2008 General Motors Corporation. All rights reserved.
Drove it around today and it's running better than it ever has. quick throttle resonse that wasn't there before. I assumed the lack of response was just traction control keeping me from spinning the tires. It's pretty snappy now. Economy is up to around 22 MPGs too. It was around 12-15 MPGs.
brodg, Thanks for the info, I am going out right now to check those grounds. I did do a wiggle test on the harness wires at the throttle body. But not on the ground circuits. It's hard to believe it would be a bad ground since it only malfunctions at 60-70 MPH, never slow in town driving, over bumps,rr tracks etc, etc. But I will check them all.
Thanks!
brodg, Thanks for the info, I am going out right now to check those grounds. I did do a wiggle test on the harness wires at the throttle body. But not on the ground circuits. It's hard to believe it would be a bad ground since it only malfunctions at 60-70 MPH, never slow in town driving, over bumps,rr tracks etc, etc. But I will check them all.
Thanks!
Ok, so I went and looked. I can't feel any ground wires connected on the back vertical surface of the passenger side head. There is a single ground wire connected to the top of the head between the #6 and #8 coils. That ground is tight and the wire seems well crimped into the the lug.
Rivieraracing
Full Access Member
Sorry to hear that the problem is still there, brodg might be on to something, I would take that info that he gave and take it to the dealership and ask them about it. They should be looking at those bulletins themselves to help themselves with the diagnosis of you rig, maybe they haven't seen it. Worth a try. I'm suprised that they can't duplicate the problem and see it on a machine, seems like everything is so computerized on these rigs that one of their diagnostic tools would be able to pick it up when the problem happens.
Dealer had it all day. They traced every wire back and found several ground connections that were either bad crimps or the lug was spread apart and had bad connections. They are keeping it over night to test drive it the morning.
No dice
Now they are on to trying the ignition switch. Glad all this troubleshooting isn't costing me anything.
Update: The tech went out with the Shop foreman. forman was driving. Tech had his scanner connected and was watching the PCM loose communication link with the Accelerator control module and to the throttle actuator module. That is why they are thinking it's the ignition switch. They are keeping overnight again to test in the cool morning.
the sage continues...
Now they are on to trying the ignition switch. Glad all this troubleshooting isn't costing me anything.
Update: The tech went out with the Shop foreman. forman was driving. Tech had his scanner connected and was watching the PCM loose communication link with the Accelerator control module and to the throttle actuator module. That is why they are thinking it's the ignition switch. They are keeping overnight again to test in the cool morning.
the sage continues...
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Got it back. They tested it this morning and it worked good for them. The thing is though that my experience with it is it only messes up when it's below 40*. This morning it was 50*.
So they let me take it home to test over the weekend. It's supposed to get back down into the 30's.
Also said that since they swapped in a test ignition switch that if it's fixed, they will not charge me for the switch, only the labor. That part seems a bit odd to me.
But if it's fixed, I really don't care at this point.
So they let me take it home to test over the weekend. It's supposed to get back down into the 30's.
Also said that since they swapped in a test ignition switch that if it's fixed, they will not charge me for the switch, only the labor. That part seems a bit odd to me.
But if it's fixed, I really don't care at this point.
wannabefastss
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check all of your grounds, if one ground is lose you will loose power like that, enentually it will get worse and it want run past 20mph. grounds are essential on these newer vehicle considering all the electronics in these vehicles. ran into this problem with my brothers 03' tahoe. ps you going to get dirty to find a couple of those grounds. seems like one to the block and the other to the frame
wannabefastss
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my bad should've keep reading
It's all good. I have a slight feeling that they did in fact find one or more marginal connections and that is actually the fix instead of the ignition switch as they would have me believe. Why else would they just "give" me an ignition switch and accelerator module? and only chanrge labor? Doesn't make much sense to me.
I did leave a copy of the TSB in the truck that brodg posted earlier. :shhh:
I did leave a copy of the TSB in the truck that brodg posted earlier. :shhh:
