electronic throttle control problem

Joined
Nov 17, 2006
Messages
4,478
Likes
6
Points
38
Location
Portland,Oregon
#1
Hey guys....I have a 2004 Chevy Tahoe, 5.3,4x4...in here that has no throttle response....I am getting the following codes...PO120...PO220...P1516....it will start and idle fine but has the fly by wire ...electronic throttle control....you can step on the gas pedal and get no response.....I am not suren if it is the control module or a tps....anyone work on these dumb things before....I am lost with thing....I apppreciate all the help I can get....thanks....Jim
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,908
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#2
Hi Jim, have :idea:seen this way too many times. Check out throttle response on DVM. Most times it is the TPS

Once had two day too check, still was tps. Had to call GM, and they thanked me for info and TBS came soon after.

Another model was communication from gas pedal sensor to throttle. That was a first. So that being said, I think you are close. 8)

As for others who read this, do research and forget french :ROFL

Can't wait for wires to come back!! A cable adjustment is quicker and more solid as a buzz line communication in my opinion.

I would try a reprom/reprogramation.

P0120 is TPS malfunction do not need a google search. Hope this helps 8)

@Jim, I know your skills, this for other who encounter this. So here is a simple link.

http://www.obd-codes.com/p0120
 
Joined
Aug 28, 2007
Messages
4,788
Likes
26
Points
48
#3
Motor driven TPS on the TB.



Foot operator throttle control actuator on the gas pedal.



A so called servo system developed mostly during WW II for radar remote location control and for the automatic pilot. Replaced conventional cables for aircraft control surfaces, in particular for much larger aircraft with extreme heavy loads for the pilots. Kind of like power steering, but here, just replaces the throttle control cable. In automotive, a dual function, key ingredients for the cruise control.

You are the man with the circuit diagrams, care to post the circuits for these key two components? Both sender and receiver are potentiometers that have a wearing wiper contact, your foot determines the output voltage that is called an error voltage, TB motor must make the TB pot follower this voltage, error amplifier is part of the PCM. You can see there are many electrical connections, the pots, and motor as well that can be the problem.

"03 Reduced Engine Power - DTCs P0120 , P0220 , P1516 and/or P1518 - 03 Model Year Full Size Trucks and Utilities with 4.8 , 5.3 or 6.0 Engines - kw CEL light low LQ4 LQ9 LR4 MIL reducedpwrmde #PIP3042A - (Aug 30, 2004)

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:

Service Engine Soon Light and / or Reduced Engine Power Mode due to any of the following DTCs: P0120, P0220, P1516 and/or P1518.

Recommendation/Instructions:

If the SI diagnosis and bulletin 03-06-04-032 did not isolate a concern, the following information may help:

1. Inspect the Yellow TAC Motor Control Circuit (581) about 1 inch to 4 inches from the throttle body connector to see if it is broken inside of the insulation.
2. Inspect S102 if there is a P1518 stored. S102 is in the engine harness and is 5.5 inches from the MAP Sensor.
3. Install that latest engine diagnostic calibrations in the PCM. Some 2003 model year vehicles have updated engine diagnostic calibrations available to address DTCs P0120, P0220, P1516 and or P1518. The title of the updated engine diagnostic calibration in TIS2000 is "New calibration to eliminate setting of P0120, P0220, or P1516 with the engine not running. Includes diagnostic enhancements for P1518."

If the above did not help, replace the throttle body and retorque it to 45 lb/in on the 1st pass and 89 lb/in on the second and final pass."
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,908
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#5
1. Inspect the Yellow TAC Motor Control Circuit (581) about 1 inch to 4 inches from the throttle body connector to see if it is broken inside of the insulation.
2. Inspect S102 if there is a P1518 stored. S102 is in the engine harness and is 5.5 inches from the MAP Sensor.
3. Install that latest engine diagnostic calibrations in the PCM. Some 2003 model year vehicles have updated engine diagnostic calibrations available to address DTCs P0120, P0220, P1516 and or P1518. The title of the updated engine diagnostic calibration in TIS2000 is "New calibration to eliminate setting of P0120, P0220, or P1516 with the engine not running. Includes diagnostic enhancements for P1518."


Yeah, what he said is true. Most often, it is the first part/ picture that Nickd kindly provided. Recalibration cannot be done without some knowledge. If the tps and wiring has been fixed, go to WOT, crank relearn, and all should be fine, don't need a tech2 for this. But often, need to reprogram after fixin the issue, here you need a dealer. Sorry Jim, cannot give better info, cuz this is the only way I have handled these very known problems,

A laptop, gmmin # and patience if another tech needs the laptop :ROFL

If all else fails, replace IAC module, but will still need reprogramming. ouch Sometimes it will work, need to do a good drive for system reset and good drive cycle, drive cycle conditions should be in your database :idea:
 

Gus

wrench
Joined
Dec 8, 2006
Messages
2,421
Likes
0
Points
36
#6
Yeah, working on these "fly by wire" systems, especially intermittents, you need a scan tool to see the inputs from the pedal sensors and also from the tps sensors......I say plural, even though it is one sensor with multiple input/outputs....

See a lot of Techs replacing whole throttle bodies, when more often than not, it's something simple....

You have a code for the pedal, tps, and module....

I have a video for you to watch, actual it's two, part one and two....

Pedal sensor is rarely the problem.....

One problem is a dirty throttle body and bore...it can stick, and cause a code....so check that first...use a wet rag with carb cleaner to clean the edge of the plate and the bore......then with the key out of the ignition, remove the neg and then the positive bat cables...then hold the cables together or jump them together with a wire for one minute...then hook up the pos first and the neg second....what this does, is resets all the modules in your vehicle, including the TAC module....

The second thing to check, is the wire harness to the throttle body.....check the contacts in the harness, and also tug on the wires, like in the video you will watch.......I go one step more...I untape the loom covering and go back 4-5 inches....I pierce one wire with my wire piercing tool and attach it to one lead of my ohm meter....the other end of the ohm meter lead I just touch the corresponding contact in the harness(don't stick it in and spread it!).......then I flex the wire to see if my reading jumps....

This is about all you can do without a scan tool.....basically, visual inspections, but more often than not, they fix the majority of the problems.....

In the second video, he shows a repair....sometimes the repair is right at the connector....you can buy a whole harness, very expensive, or you can make the repair the way he did, or, pop out the connector, and bring it to any GM shop and get a replacement connector.....

Hope the video helps you out...

http://www.youtube.com/watch?v=U2DjMcM_Quk
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,908
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#7
@Gus, forgot the T or just my fingers pressed on the I in said module. Also if you have access to a dealer, you must be aware that reprogram is costly.

So check wiring, if not, you will throw parts at this all day for nothing :idea:
 
Joined
Nov 17, 2006
Messages
4,478
Likes
6
Points
38
Location
Portland,Oregon
#8
it is fixed.........Thanks guys for the help....it was the yellow wire on the tps....it was broke inside about 1" back from the connector....Gus...I unhooked the battery cables like you suggested and reset the modules....it drives fine and seems to be fixed....thanks again for all the help....Jim
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,908
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#9
No, sh@t, so is there gonna be a recall on this??

Anyway, happy for you Jim. Did you find the drive cycle I talked about, or it just ran fine after wire repair?
Obviously, if was only a wire connection/split no need for what all other crap I said/wrote.

Sometimes a guy tries to wrap his head around a problem like this, not easy.

Maybe dealer will have a new fix such as a new wiring harness, but not likely ouch

Ps, thanks for the fixed reply.
 

Gus

wrench
Joined
Dec 8, 2006
Messages
2,421
Likes
0
Points
36
#10
There have been TSB's about wire harnesses that are too tight, and when the engine moves forward and back, this flexes harnesses.....never had recalls for them, just TSB's.....funny, but most of those wire harnesses went to the TPS sensor, even the throttle bodies that had cables.....
 
Joined
Aug 28, 2007
Messages
4,788
Likes
26
Points
48
#11
Motor mounts? We use to use a minimum of 16 AWG wire in automotive, not because of its current handling capability, but because it was far more robust. Now finding 28 AWG wire in these things. How thin are these wires?

Then the price of copper, son wanted a water softener/filter like mine using all copper, went with plastic that would break when trying to change a filter no matter how tight it was secured. Recall mine around 20 years ago was around 40 bucks for everything. Was a bit shocked when his bill just for copper came to 360 bucks!

One thing that did not increase by a factor of nine, is our paychecks.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,908
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#12
Sometimes, I cut the tie wraps or remove the bolts holding the harness's, gives them more leeway.

Funny, I don't see that often, only on GM.

Hoping the dealer has a goodwill account for this cuz it is starting to be ridiculous.

Had a caddy in my bay, under the battery, another stretched wire, pink or purple, doesn't matter. Same situation.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
9,908
Likes
180
Points
63
Location
St-Hyacinthe, Quebec, Canada
#13
@Nickd, I agree 100%, last time I bought butter, and looked at my inflation rate up here, no go!!

How can a guy get ahead? Hard work and hurt hands, this is a hard trade.

When i found out that my gov is going to downsize minimum wage here in august by 55cents, and projecting to downgrade to 9$ per hour. I freaked, they say it will produce more income for low salaries homes. Bullsh@t!!

Do want not to scrap this thread, so I will ruminate while venting my frustration on my oven that blew a connector/switch and no one has the right parts. Just spent 60$ for nothing and lost receipt :ROFL

So here is a good tune for every awesome guy here.

http://youtu.be/5XcKBmdfpWs

@MobilDan, still trying to master solo just before the blond guy shows his credit cards, even though I have seen this group 5 times :ROFL