2008 Grand Prix 3.8l ignition interlock issues?

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#1
Howdy, folks, long time no see!

A friend of mine has the above mentioned vehicle. It is displaying the message "starting disabled due to electronic throttle control", or something very similar, when he engine dies, which happens quite regularly. When this occurs, the engine may restart or, more than likely, turning the key interupts all circuits and does nothing. An additional messge indicating the engine is derated also appears. CEL illuminates when this occurs, but never while driving, until tonight.

Tonight the CEL did illuminate, and threw codes for ignition module, ECM, and MAP. She thinks two of the three codes were 0601 and 0606, but the Pep Boys lackey didn't elaborate, and she was trying to look over his shoulder for any intel she could glean.

She has been made aware that there is a recall on the vehicle for something concerning rhe ignition key, which may or may not have anything to do with this issue. The key is a factory Pontiac key, her only one, and looks like a standard key with a large plastic cover at the end. Wiggling the key or tapping the dash in that area does nothing. Neither does it respond to colorful language.

This sounds to me like an interlock/immobilizer issue. I remember previous generation security systems being troublesome, but perhaps I assume too much. Any ideas?

Thanks, all!


Fred Malito
 

nickb2

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#2
Code P0606 is for TAC(throttle actuator control). The flow chart seems to want to reprogram before PCM replacement.

Also, I have seen many electronic throttle actuators with stripped gears or heavy carbon build up or loose connections at TAC module connector. Pull on them lightly to see if any are loose.
 

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#3
Thanks, Nick! I'll take a look at the files as soon as I can get to a computer.

The more I tried to read about this on the mostly useless Google searches, the more I saw that I was completely off about the security system. I did see a lot of people reporting PCM replacements. So much for my brilliance!

I will check the TAC as soon as I can get my little fingers on it. Never having worked on the late model 3800s, this will be on the throttle body as a TPS would have been mounted previously, I assume? Any concerns removing, inspecting, and reinstalling it, i.e. clock position, timing to throttle plate, or something else that would make me not want to just remove it for the hell of it?

For that matter, this then likely has nothing to do with the throttle pedal sensor then as that would be a different code?

Thanks, bud!

Fred
 

nickb2

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#4
Check attachments for more details. 8)
These drive by wire TAC's seem to have screws that can be removed easily to inspect the gears. Second picture may not be exactly what you will find but similar, look for a dirty bore and striped gears.

The first picture should be yours for a 2008 grand prix. http://www.apdty.com/searchitem.epc?lookfor=S20012&s_temp_transfer_key=_48O0GEOAV

What seems to be the failure of the Electronic Throttle Body is the plastic gear drive. A common problem of the throttle body bore has been a build up of gases from the EGR and PVC systems, combined with heat causes a formation of gummy residue. This gummy residue often restricts airflow causing poor or hunting idle and even stalling conditions. This residue can become so built up that it causes the throttle body plate/blade to stick, striping out the gear drive in the throttle body. - See more at: http://www.autorepairinstructions.com/?p=140#sthash.G6n0ly9L.dpuf
 

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#5
Excellent, and thank you! I have made arrangements to take a look at the car later this week and will post my findings. Hopefully we are barking up the right tree, and this requires no further expenditure/diagnostics on her part.

While I have your attention, anything special about refilling the coolant system post-replacement, if that turns out to be necessary? I assume there's a bleeder. I'll be doing a complete drain and fill, as I am operating on the assumption that it's been overlooked.

Edited to add: how does the throttle body you linked to compare to AC Delco parts, out of curiosity? I had no luck finding anything aftermarket, and AC Delco is special order for my region, and a week away due to holidays.

Thanks again, and Merry Christmas!


Fred
 

nickb2

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#6
I wouldn't know how it compares to ac delco. Just thought it was cheaper than OEM.

No special procedure to speak of for refilling the coolant. You will most likely not lose much. See attachment.

See screen shot for oem part number and price.
 

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nickb2

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While I am not saying it absolutley the TAC, it is worth a look for those gears and gunk build up. Gasket seems reusable if not torn or scratched. E-bay and amazon sell same item for 280-300$. Oem is over 400$. Standard company has always been a relatively good company in the past, they mass produce alot of ignition modules and other injection sensors and such. Been around for awhile. http://www.smpcorp.com/en/

The presence of P0601 or 606 code does indicate internal PCm problem as stated in the previous attachment I posted. However, since she cannot be sure, would be best to get codes again, or buy a cheap scanner for home use to diagnose this and future vehicles. ;)
 

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billr

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#8
The SMP is about $200 from rockauto, that's what I what get. Standard Motor Products (SMP) has been an aftermarket "name-brand" for many years. Yes, it could be related to the pedal sensor(s), it is a system that is causing problem, trouble-codes try to point to an individual component, but it may not be an exact diagnosis.
 

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#9
@Bill, is rock auto a online buying site or an actual american parts retail store? Like Autozone or pep boys? Up here, we are limited to Carquest or NAPA. And in the unlikely event that Canadian Tire may have it, they are the sunday parts goto ppl.

I would imagine this pedal sensor can be checked like a TPS. Could not find a resistance chart for it though. They usually have their own trouble code. It was stated that the lady did not get a print out or have the time to write down all the codes. So we are kinda shooting in the dark.
 

billr

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Rockauto is an online broker for other suppliers. They don't really stock or ship anything, are really just hooking you up with other sources, but are there to make good on any problems with an order. I consider rockauto.com to be a reliable "supplier" with good prices, but not all parts are available (inspite of their slogan!); and you will have to pay shipping. Sometimes I will pay $5 to ship a $5 part, but if that same part costs $15 locally, then I'm still better off ordering from RA if I have time.

I'm thinking that by '08 the PCM diagnostics were sophisticated to try distinguishing between a problem in the actuator from one in the pedal assembly, but I'm sure there could still be some confusion, so best to do more trouble-shooting and not just throw parts at it. It looks like the stripped-gear is common and easy to check, I would start there.
 
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#11
A quick update; I got the chance to play with this thing, and found that the sensor was indeed removable from the throttlebody with four tamperproof screws. However, what I found inside was quite unlike the pictures that are online. The sensor and motor are separate; the motor is on the throttlebody and all of the gears with it, and the gears are all metal. They look to be brass or bronze. The sensor comes off of that assembly and is completely sealed. Also the wiring harness is very sturdy where it mounts with a locking tab and a cam-lock harness, which is quite well sealed from the environment.

The one thing that I did notice is that this is mounted a mere inches from the exhaust crossover pipe, and I am curious as to how well it holds up to those extreme temperatures. We're going to try another unit on the vehicle to see if it cures problem, but at this point I am becoming less and less convinced that is the most likely suspect. I'll repost once I see what happens with the new unit. Cheers!


Fred
 

nickb2

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#12
This is where I hate giving advice on internet. That module is quite expensive and may not be the problem and most likely cannot be returned. I remember this had some codes which the lady was not sure of but could have been P0601 and 606 right? Now the 606 one was for PCM internal glitch if memory serves right.

I think this needs more diagnosis before putting on hundreds of dollars of investment when not 100% sure of the outcome.

I think it would be prudent to invest in a proper scan tool first to get those codes or go back to pep boys or where ever she went to get it scanned and make damned sure she gets a write out of codes.

This should have been done at first since I remember the original post said she only glimpsed behind shoulder or something to that effect.

Went back and read, here is the quote
She thinks two of the three codes were 0601 and 0606, but the Pep Boys lackey didn't elaborate, and she was trying to look over his shoulder for any intel she could glean.
I would do this before opening that module. Get those codes.
 
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#13
Nono, fear not, you are not leading me astray. In fact I am waiting for my friend to return to work after new years to see if we can determine what else is wrong. She tried to get to the dealer, but on the day of her appointment they decide they were to busy to see her. I got the part coming early due to he holidays as it was a week away. We'll see where it goes; I am well aware the risk of throwing parts at a problem!