SOLVED: 2008 Envoy Denali TPMS issues

[56napco]

2008 GMC Envoy Denali (short wheelbase), replaced all four TPM sensors in February 2016 with AC Delco sensors. Immediately after replacing the sensors the dash light came back on and the LF stopped reading intermittently, worse when it was colder (below 40F). The truck stays inside in a heated garage. In March, I had the LF replaced again at the dealer and the light came on again. First the tire pressure reading is shown, then after driving a bit more just dashed lines show up, then after a little farther it starts reading again. Then after doing a key cycle the light goes back off and stays off. The other wheels don't have this issue and the dealer would not diagnose it unless the TPMS light is on and the sensor reading is dashed lines. We have taken it in several times, first all they did was re-teach the sensors and then lastly replaced the BCM in April after they were able to get the DTC for the left front. After the BCM replacement there have been no TPMS lights all summer until recently when the temps began cooling off over night in the 50's. After about 15/20 minutes of freeway driving (65-75mph) the TPMS light will come on, left front will be dashed lines on the DIC. Turn off the freeway onto a 2-lane county road (55mph) and the left front will begin reading again but the TPMS light stays on. In the afternoon, after work, ambient air temps in the 70's/80's no TPMS light at all. Anyone else have issues with just the LF wheel sensor? Is the receiver module starting to have issues in the tailgate? All lift gate functions work, wiper, defrost, keyless entry, etc. I have rotated the tires a couple times since the sensors were installed and they register correctly when you go through the re-teach procedure in the owner's manual.

**should've have stated when the dash light comes on it flashes and the DIC says "Service Tire Monitor" then after about a minute the dash light stays on solid. According to GM document #07-03-16-004B this flashing indicates a system malfunction but does not elaborate any further and what is malfunctioning other than the sensor may not have transmitted info for 18 minutes of driving.

 

[xavierny25]

I have had the same issue with my voy for the past 1yr and 1/2. Although I haven't replaced any of my tpms and I know I should it's very intermediate and does happen more at high speeds and with sudden changes in temperature. It also is just the LF sensor that has the issue no matter which tire I rotate to that location.

So I'm thinking it's not the sensors them selves but something going on with the module that's reading the sensors.

We'll see if anyone else may have something to add.

 

[coolasice]

Could a bad /cracked/broken wire to the lgm cause this problem?

 

[56napco]

A bad wire or connection could very well be the culprit but not to have an issue the entire time from April until about a week ago, a rubbed through wire would seem to act up regardless of the outside temperature and possibly affect keyless entry, wiper, etc. Last night I unplugged the LGM and reconnected it and had no lights this morning, will continue to monitor it and once I get enough free time I'll check over the harness closer too.

 

[DAlastDON]

A bad wire or connection could very well be the culprit but not to have an issue the entire time from April until about a week ago, a rubbed through wire would seem to act up regardless of the outside temperature and possibly affect keyless entry, wiper, etc. Last night I unplugged the LGM and reconnected it and had no lights this morning, will continue to monitor it and once I get enough free time I'll check over the harness closer too.

A broken wire partially making contact will however be affected by temperature. Metal expands with temperature increases then contracts when the temperature decreases.

 

[56napco]

Yes, I am well aware of how wires and other materials expand and contract with temperature changes. If this was the case it should happen every day when parking in the garage and then driving in the colder temps, it however does not. The same goes for vibration, if the wire was only making intermittent contact, the last 10,000 miles should have triggered something. As I said, once I get some free time I will inspect the harness more closely.

 

[56napco]

Checked the harness at the body to gate joint and found no signs of wear or chaffing of wires and no loose connections. Took the Envoy on a 1000 mile trip this weekend, temps in the 40's in the morning and 70's in the afternoon with rain over night. No TPMS light until we were a couple hours from home and then it was for the RH front wheel, showing only dashed lines. This happened after 6 hours of 4-lane and 2-lane non-stop driving and no TPMS lights the entire trip. Stopped for gas an hour later and the light stayed off for at least 45 minutes, then RH front again showed dashed lines.

 

[northcreek]

My only question would be...where did these sensors come from? there are a lot of pseudo ACDelco sensors coming from China. A member here(another thread) just bought four that would not program.
A long shot but,what kind of tires are you running? perhaps the steel belts are configured in a way to cause shielding.....Mike.

 

[Mooseman]

And even if you got them from the dealer, it could just be a dud. On my new at the time '08 SV6, all four failed early and one of the replacements also (all under warranty at the time).

 

[56napco]

All sensors are AC Delco, I got all 4 of them from Rock Auto, then got one from Amazon when I had the first one replaced in the LF wheel, then that same one was replaced with one from the dealership before they replaced the BCM. All program and teach just fine and are the same part number and say made in Great Britain as the sensors that were in the wheels when we bought the Envoy. I have rotated tires several times and go through the teach procedure each time, two different dealerships and a tire shop have also put them through the teach procedure.
Tires are Bridgestone Dueler Ecopia- the dealer we purchased the truck from had them installed well before we bought the truck. When the first sensor went it was the RF and about 3 weeks after we had the truck in December '15.
Drove fine last night and today, no TPMS light, the only thing I did after checking the wire harness was disconnect and reconnect the liftgate module.

 

[northcreek]

You have really done a great job trying to track this down. It's a shame that all the expense and hard work is not reaping any rewards.
My wife's Equinox was only 2 years old and started having lift gate issues(not effecting tpms) and it drove me crazy, what I finally found was that road salt had followed the gate harness to a "non o-ring connector" which GM must have felt was OK because it was in the gate. As bad as it was, everything worked except the latch...I spliced and heat shrunk all the wires. Not saying that this is your problem but, I thought it was worth a mention.Please keep us informed...Mike.

ps any pics of that NAPCO?

 

[56napco]

Thanks, still chasing this one and haven't bothered to take it back to the dealer and go through that mess again. Envoy was in the garage as usual, this morning we had temps around 30F and my wife drove the Envoy to work ~45 minutes @ 70mph, no TPMS light. So I'm beginning to lean toward the liftgate module or a bad connection there. The last time I disconnected and reconnected it the TPMS light stayed off for about 2 weeks. Another thing, with the current sensors there has never been a rear wheel causing the light, always a front wheel.

Attached is a picture of my Napco, patiently waiting it's turn to be restored. Currently up north being used around the cabin from time to time.

 

[56napco]

Quick update on this issue. The TPMS light has been coming on more and more frequently with the cold weather setting in. The Envoy usually sits in the garage during the week, ~50 degrees, and my wife and I take our Cobalt to commute to work most of the time. The RF seems to be acting up more than the LF now and the RF was the very first to give us trouble last December when this all started happening. Last week I rotated the tires (fronts to rear and rears to front), retaught the sensors and was really hoping the TPMS light would follow the tire so it would narrow it down to the sensor. That's not the case, this morning it was 11 degrees outside and we made it a whole 10 miles before the light came on and it was the RF showing only dashed lines. None of the other wheels stopped reading. Its about 40 minutes from home to my wife's office and sometime close to her office the RF began working again. Could an ABS sensor in the wheel bearing cause interference? The only thing I can say is consistent is the light comes on in colder weather.

 

[coolasice]

Maybe a poor receiving antenna in the lgm?

 

[56napco]

Could be, I checked the receipt from the dealer and they did replace the LGM this past spring, not the BCM as I had thought. I'm going to see if the dealer will replace it again, hopefully under warranty, since it isn't following the wheel and only stays with that RF corner. The only other thing I've noticed is every now and again it will not lock with the keyless remote but I haven't tried changing batteries in the remote either since this too is intermittent. We'll see what the service manager says...

 

[56napco]

Envoy goes to the dealer this week, doubt it will be covered under any warranty though. Had sub-zero temps this morning, only LF wheel came on this morning. Will update again after the dealer has a look at it, have a bad feeling they won't be able to figure this one out. The first time around they had to call GM to narrow it down to the LGM.

 

[56napco]

The dealer had the Envoy for two days and drove it multiple times and the TPMS light would not come on for them. All they were able to do was pull codes for the LF and RF TPMS lights but couldn't diagnose it any further without the light coming on for them. The light did not come on this morning either on the way to work. Does anyone have a wiring diagram for the liftgate harness? Ground locations?

 

[Mooseman]

Check the link in my sig for the manuals. Should be in there.

 

[56napco]

Thanks Mooseman. The TPMS light came on today on our way home. Swung into the dealership and they checked it out. They were able to get signal from all 4 wheel sensors and connected to the liftgate module and found it was transmitting all 4 signals. They said it is a serial signal and only uses 1 wire to transmit them. So, they're contacting GM tomorrow to find out whats next to troubleshoot.

 

[xavierny25]

Please keep us/me informed on what happens next as I'm going through the same situation.

 

[Mooseman]

Whenever you get an intermittent light like that, get to a dealer right away and keep the engine running because as soon as you turn it off, the code erases itself. Just explain what is going on and they should send a tech out with the scanner. I had the same issue with the Stabilitrak and I was able to pull the code only while the light was on.

 

[56napco]

So far no reply from the dealer. The TPMS codes will stay stored without the light on but for this issue they couldn't do anything without the light on. I should have time to do some troubleshooting of my own this weekend now that I got the schematics downloaded. One strange thing I've noticed is the TPMS light will come on after at least 10 minutes of driving at 65/70 mph, sometimes it take a few minutes more. If we only drive around town the light will not come on. Our commute to work, for example, is 40 minutes of 70mph and the light will come on and the RF or both RF and LF will read only dashed lines. When I slow down and pull into the office park (30/35 mph) to drop my wife off at work the pressures will begin reading again and continue working properly for the rest of the drive, no time spent over 60 mph. Not sure if speed is a contributor or if the wheel bearings are creating noise that is blocking the TPMS signal or there is noise on the serial bus from another sensor. Still waiting to hear what the dealer has in store next.

 

[northcreek]

Man, that sure is strange, almost like someone put a handful of aluminum foil strips in your tires (used that in WWII (chaff/window ) to disrupt radar signals).
Seriously though if the dealer can't figure it out with all that they have at their disposal you could end up living with this or doing a "TPMS delete " good luck.

 

[Mooseman]

I do believe there is a sensor in each wheel sensor that detects wheel rotation for some function. Maybe that or the batteries are starting to go.

 

[56napco]

I have a tough time thinking the tire pressure sensor batteries are to blame since the light doesn't follow the wheel when the tires are rotated. It was a balmy 20 degrees this morning and it took about 20 minutes for the TPMS light to come on today vs. 10 minutes when the temps are colder.

 

[56napco]

The service manager at the dealer called today, GM's feedback was to have the front 2 sensors replaced and see if that solves the problem. GM list price is $92.50 per sensor. They are good enough to let me bring my own GM parts and they will install them but if it doesn't fix the issue then I'm still out over $100 just in parts.

 

[Mooseman]

As usual, they can't even diagnose their own stuff.

 

[northcreek]

The service manager at the dealer called today, GM's feedback was to have the front 2 sensors replaced and see if that solves the problem. GM list price is $92.50 per sensor. They are good enough to let me bring my own GM parts and they will install them but if it doesn't fix the issue then I'm still out over $100 just in parts.

Wouldn't moving the rears to the front prove/disprove their theory?

 

[56napco]

That's what I'm going to do next but not go through the sensor learn procedure. My guess is I'll get a light for the RR by doing this. Either way, if the light came on for the RF wheel, I then rotated tires (moved front to rear, rear to front) and performed the sensor learn procedure and the RF still triggered the warning light to come on but never got a light for a rear wheel the sensor wouldn't be the issue.

 

[56napco]

So, tonight I noticed something different happening. The TPMS light typically comes on after about 10 minutes of driving on the freeway. Tonight, after we left my wife's office I noticed the TPMS light wasn't coming on like usual. I also noticed that only the DRL's were on since it was light enough for the headlights to come on yet. I kept watching and eventually the headlights came on, or I guess the rest of the running lights and dash lights since the DRL's are the low beams anyway. 10 minutes after the headlights came on the TPMS light started flashing and both the LF and RF tire pressures were dashed lines. So I have a couple thoughts, first there is something going on with the headlight circuit since the headlight switch is used when getting the truck into learn mode for the tire sensors or second the LED license plate bulbs I put in after we bought the truck last December are causing noise or a harmonic on the circuit causing the signals to get interrupted. So, I've got a few things to dig into now this weekend again.

 

[Mooseman]

I'd be looking at the schematics and see if the wiring is somehow related. Maybe a bad ground or the power to the TPMS system.

 

[56napco]

Thursday night I swapped out the LED license plate bulbs with incandescent 194's. No TPMS lights since but will be keeping an eye on it as always. The temps have warmed up here too. Also, there is quite a bit of info available in regards to LED bulbs creating radio interference and causing issues on electrical circuits, especially the cheaper bulbs. So far, so good.

 

[northcreek]

Wouldn't that be crazy, if it turns out to be something that simple....

 

[56napco]

Yeah, never would have thought a couple stupid LED bulbs could cause something like this. Took the LED's out on Thursday night, haven't had any issues since with TPMS or keyless remotes. Thinking back, it makes sense now of course, I put those LED's in about a week or two after we bought the Envoy and the TPMS light started acting up a few days after that. If anything else acts up I'll report back but thanks for your help guys!

 

[northcreek]

I'm surprised that this never came up before, I mean, if you look at the "what came in the mail thread" it's bulbs,bulbs,bulbs

 

[56napco]

Guess I missed that post, I've spent hours searching the web and multiple other forums and nothing mentioned LED bulbs in the license plate lights before. I've seen many posts about LED bulbs in the instrument cluster or people asking how to eliminate the TPMS warning light bulb though.

 

[northcreek]

Sorry, what I was trying to say was, with all the people buying/installing so many leds on this site. I'm amazed that this tpms issue never surfaced before.

 

[Mooseman]

Probably just one particular brand or type that causes it and there are lots out there.

 

[56napco]

I got ya now, I didn't think it would be the issue since I have my Yukon XL switched over to LED's on the interior, DRL's and a few other marker lights, but that truck doesn't have a TPMS and I never had radio reception or keyless entry reception issues.
The LED bulbs I removed were from superbrightleds.com and there are some more expensive bulbs available from Sylvania and Cree which have a bit better reputation and you get what you pay for. Cheaper bulbs will be noisier than a higher priced bulb that have higher quality LED drivers. I'm still going to purchase a couple bulbs with Cree LEDs and drivers and see what happens.

 

[xavierny25]

@56napco I know you've seen dashes/lines and the flashing. But have you ever seen this I've been monitoring this on wheel for a while now.
I will be going back to stock bulbs in the license plate location as you did and see what happens. Like you I do get dashes after going 70mph + for 30min+. But in the pic you can see the pressure is actually a little high but it's showing low. Like wtf is that about.