2014 Z51 M7, around 32k miles, with mag ride etc., 265/35ZR19 PSC2 fronts and 305/30ZR20 PSC2 rears. Looking for some insight ...

Recently, two (bad) things have happened:

1. The front left TPMS sensor (which had a perfectly good battery, but was massively under-reporting pressure) finally died and now does not report any pressure at all (so the TPMS dash warning light is always ON)
2. I've noticed that the car is turning on the stability warning light (car over squiggly lines, yellow, in the speedometer) even at moderate speeds in e.g, highway onramps, and the rear feels really squiggly, almost unsafe to drive. This happens in Touring, Sport and Track modes. This was NOT happening back when the front left tire was reporting low pressure (not like now, where it's completely absent from the TPMS display).

Is #2 happening because of #1? I thought I had read in the forums (in a discussion re track days and TPMS) that the C7's stability program ignores TPMS, but maybe that's not the case.

Thanks for any insight you can provide.

 

yes, I had the exact same problem when I got a 2nd set of wheels and I couldn't get the sensors to work. The stability control kicks on ALL THE TIME and it is downright miserable to drive.
I agree it feels unsafe because it kicks on when you aren't even close to pushing the car and it almost pulls you in a different direction.
IMO this is some sort of software glitch because there's no logical reason for the stab cont to do this when you have a tpms issue.
Once you solve your tpms issue the other one will go away.

 

Thanks -- I have been holding off on fixing the TPMS because these are new, forged wheels and my old tire changing guy (who was AWESOME) is no longer in business :-( ... Gotta now risk taking it to another place. Oh well, and I appreciate your confirming with the same experience -- it is downright scary when the car behaves like this.

 

AEK, if you're worried that a new, unknown-to-you tire changer might screw up your wheels dismounting and re-mounting the tire (a legitimate concern), he may be able to replace the TPMS simply by letting out all the air and gaining access by pushing the sidewall in. If that works, then no need to dis- and re-mount and risk wheel damage.

 

Dear AEK:

Fix the known problem and then diagnose the new issues.

They may just go away by themselves after.

Having a malfunctioning TPMS sensor replaced is fairly easy to accomplish.

Regards,

The Beav

 

Thanks all -- I'll either be crying at my damaged wheel or relieved once I get the TPMS replaced -- I dunno if on such stuff tires and large wheels, that they can push the sidewall out of the way to just change the TPMS -- we'll see.

 

Go to TireRack's website and look for their recommended installers. Find one near you by zip. At least then you have a fighting chance that they will be competent.

 

Without special tools, the tire shop will not be able to push the sidewall in enough to change the TPMS sensor. I have done this many times using 600 lb bar clamps, but most tire shops are not going to have anything to do this. The sidewalls are way too stiff to do this by hand like they can on "normal" car and truck tires. If the OP lives near St. Louis, I would be happy to do this for you.

 

I agree... fix the known issue and precede from there if needed. What you did not say, or I missed it, was how old your car battery is. When they start to go bad all sorts of gobble-de-gook can start to happen. I'd consider checking that after the sensor replacement. (and, clean the battery cable connectors). All the best, in any event.

 

When the TPMS needs servicing you can't turn off the Stability Control it is forced on (unless there is a failure in the Stability Control system) to prevent an accident due to a zero-pressure tire. I suspect they do something similar to the method used on the C6. With the light on the stability control system would turn on and then limit the car speed to 55 mph in turns. To do that it automatically applied the brakes when the steering wheel was turned if the car speed was above 55 (I had this happen with my C6Z when a sensor stopped broadcasting while I was going through T4 at the Glen at 120+ and all of a sudden the front brakes were applied).

I doubt the stability control is causing your problem but an actual tire problem could cause stability issues that might cause the system to react. Have you checked the tire pressure in all four tires, especially the left front tire?

Take the wheel to a good shop and have them replace the sensor with a GM sensor. I forget which company makes the GM sensor but you want a sensor from them or from GM, not any other company. There are a number of aftermarket sensors that work for a while and then fail. Even though they are warranted you still have to pay to have the tire broken down and if the sensor fails again the warranty won't cover it. It may be more expensive to purchase a GM sensor but they do last a long time.

As for stability ignoring TPMS it does if all four sensors aren't installed and the tire pressure readout is a dash for each tire. Drag racers found out that swapping rear tires for the strip caused the stability control system to turn on unless the strip tire/wheel combo had sensors installed or the front sensors were removed as well.

Bill

 

I agree with Bills advice! Schrader makes the OEM AC Delco TPMS sensors. Schrader sells parts under their own name that are the same as the OEM AC Delco parts with a different part number. I have had good experiences with both. The Schrader brand is usually less expensive. Again, if you are close to St. Louis, I have the TPMS reset tool and the ability to swap the sensor with no damage to wheel, tire or sensor.

 

Inexpensive GM on Amazon -

 

All:

Am following up -- in this post I can confirm that all of the rear-end unpleasantness went away (immediately) once the bad left front TPMS sensor was replaced and the TPMS service required lamp extinguished.

Funny story -- I fixed the bad sensor, the TPMS system problem self-cleared after about 20 miles o the highway, I tested a few on/off ramps, all good ... and then the TPMS alert lamp came back on because (now) the right front TPMS had failed (and the rear-end problems immediately came back). Finally got the right front TPMS replaced and now the car is working properly.

In my next post, I'm going to pass on my hard-earned TPMS knowledge.

 

And so it begins. If memory serves me, 1+1=2. That means you have 2 more sensors that are likely failures sooner or later. Probably sooner since they are all 10 years old. So no. Not funny. At that age, I would have replaced ALL. You don't replace one shoe if one wore out, do you?

 

OK, I'm going to park my heard-earned TPMS knowledge in this post for my and the forum's benefit. I will make corrections later if/when errors are detected.

Background:

I have TPMS-equipped cars from at least six auto manufacturers, and several of these vehicles have multiple sets of wheels/tires with TPMS sensors. I also typically keep my cars for longer than a few years, and so I have experienced TPMS failures (always, the TPMS sensor or its battery going bad), and I also prefer to drive without the TPMS alert light on in the dash. I've "moved" wheels & tires from one vehicle to another (obviously the same bolt circle, etc.) and I've swapped wheels and tires on the same vehicle (e.g. for wheels with snow tires in the winter).

Note: When I refer to the "TPMS alert light", I will be only talking about the TPMS system failure indicator, NOT the low-tire-pressure warning light.

Understanding TPMS sensor operation and the TPMS sensor business

As best I can tell, "direct" TPMS (i.e., each wheel has a TPMS sensor) systems pretty much only transmit data and do not receive any data when at operating pressures (above 10psi). They typically transmit the tire's gauge pressure, as well as perhaps also temperature and the battery status (OK or LOW -- they can't transmit once the battery is dead). They transmit at 315MHz or 433MHz, and may use different protocols based on what kind of vehicle they're being used in. If anyone has a better overview of how TPMS systems vary from manufacturer to manufacturer and over time, please post a link!

TPMS sensors can be woken up (aka "activated") at any time via an appropriate signal: "The majority of TPMS sensors are activated with a low frequency (LF) signal (125 KHz). This LF signal varies from vehicle to vehicle (some require more power than others) and forces the sensor to transmit." Note that waking up is not the same as receiving any data -- it's just a signal to wake up and transmit its data. This is what happens when you buy a cheap ($20) TPMS tool that helps your vehicle "relearn" which TPMS sensors are at which corners of the vehicle -- the vehicle is in a (re-)learn mode, and it needs to learn the ID of the TPMS sensor at each corner (plus a spare, in some vehicles). And to do that, each sensor must be woken up / activated in a sequence (usually LF, RF, RR, and finally LR).

The ID is typically an 8-digit hexadecimal number, like 2F34D572 -- engineers write this is 0x2F34D572 or 2F34D572h ('0x' and 'h' stand for "hexadecimal"). TPMS sensors come with their own IDs from the factory (if pre-programmed). Some/many sensors can have their IDs reprogrammed.

Programming a TPMS sensor is not a trivial task and new TPMS programmers retail for $100 or more. Programming a TPMS sensor does several things:

1. It configures the TPMS sensor to broadcast at the correct frequency (315MHz or 433MHz) for your vehicle.
2. It ensures that the sensor follows the correct protocol for your vehicle.
3. It assigns an ID to the sensor (assuming the ID can be changed).

An unprogrammed sensor will never work in your vehicle. The sensor must be programmed first!

There are factory / OEM TPMS sensors (e.g. Schrader for GM, as mentioned above), and aftermarket TPMS sensors (e.g. Schrader's EZ-Sensors, Autel's MX, MAX T.O.T.A.L Max Select Pro, Alligator, WePro, Bosch, etc.). Most aftermarket TPMS sensors come unprogrammed, and some vendors (e.g. on eBay) will preprogram the sensor for your application (vehicle year, make and model). I do not know if an OEM sensor (e.g. a GM/Schrader sensor) is preprogrammed -- if GM has the same protocol across all its vehicles, then that should work with any GM vehicle, regardless of what the sensor's (preprogrammed at the sensor factory) ID is.

So this all has an interesting effect on tire sales & service -- since a (preprogrammed) OEM sensor (e.g. for GM) may not work on another model of vehicle, there's been a rise in aftermarket, programmable TPMS sensors. With a "universal" TPMS sensor and a proper TPMS programmer, a tire shop can stock a single sensor, and when a customer shows up, they program the sensor based on the customer vehicle's year, make and model. Some tire shops do not charge for programming (and hence, many people don't understand that programming is required in these cases), others charge for it.

This is complicated by what kinds of tools are available to program the aftermarket sensors. As an example, the (IMO) excellent Autel TS508 TPMS tool (around $180 on sale) can program Autel MX sensors, but cannot program any other sensors (It can also activate sensors, read IDs over OBDII, etc.). So, a tire shop could stock only Autel MX sensors, solve every customer's TPMS replacement problems with a new Autel MX sensor preprogrammed to their year/make/model vehicle, and no one would be the wiser. And unless the customer asked what kind of TPMS sensor was fitted, they would never know what brand/model was used, and neither would anyone else until the TPMS sensor was removed an inspected. Assuming the TMS sensor lasted a good while (ten years seems to be the expected life for a good sensor), everyone is happy. Note that if it's suddenly impossible to get Autel sensors, said tire shop will have to get some alternate TPMS sensors, and a different TPMS programming tool. So the tire shops have to decide whether they want to invest in more expensive TPMS programming tools that cover a wide range of aftermarket manufacturers, or just go low-budget and stick with one (or just a few) brands of sensors (and programmers).

Note that I am assuming that the protocols to program the TPMS sensors (separate from the protocol that the TPMS sensor follows when it's broadcasting pressure/temperature/battery status) differ wildly from one TPMS manufacturer to the other. It certainly seems so, from what I have observed programming sensors from different manufacturers ...

TPMS Programming Gotchas

First, TPMS sensors follow a standard that says you can only reprogram them when their measured pressure is under 10psi (or is it 7 psi?). With this low pressure registering in the tire, the sensor is willing and able to be reprogrammed.

Ah, but now we gt into some interesting scenarios. Suppose your vehicle can only keep track of one set of TPMS sensors (hence, 4 distinct IDs) and you like to swap your wheels out in the winter. On my 2008 Ford truck, the vehicle computer can only "remember" one set of wheels & tires, so I have to force a TPMS relearn when swap from summer to winter wheels and tires. To make this happen seamlessly (i.e., not having to relearn when changing from summer to winter or back), each summer wheel/tire needs to have the same ID as its winter wheel/tire "twin". But sensors come from the manufacturers with unique IDs. So how do you get around this? You have to reprogram the sensors in the winter wheel/tire set with the IDs from the summer set!

Remember how I said that TPMS sensors are transmit-only devices (at least, when they're operating normally)? Well, this means that there is no way (that I know of, maybe the very fancy tools do this) to read the make and manufacturer of the sensor itself! This means you must already know what sensors are in your vehicle so that you can tell the TPMS programming tool what sensors are present. Otherwise you're SOL because you can't get the whole programming thing going.

Assuming you know which sensors are fitted in the winter wheels, you need to get the IDs of the summer wheels. Luckily even the most basic TPMS programmers can "activate" a TPMS sensor and read its ID, the pressure, the temperature and the battery level (if supported). You can also pull the IDs from the vehicle via OBDII if your tool supports this.

So, assuming you can program the TPMS sensors in your winter wheels/tires, you can now use the TPMS programmer to (re-)program each TPMS sensor for the vehicle year/make/model, AND you also specify the ID you want for that sensor.

Note that TPMS tools can program sensors one at a time, or in a batch mode, using random IDs, IDs copied from other sensors, or IDs that you can manually input.

Wrapping Up

Here's a list of things I learned and look out for when doing TPMS work:

1. I like the Autel TS508 tool (it has a good UI, it has a powerful RF section, it connects via OBDII to read existing IDs, etc.). But it can only program Autel MX sensors.
2. I also have an ATEQ VT37 (universal) TPMS programming tool that can program a wide range of sensors. It's nowhere near as nice a tool or user experience as the TS508, but it got the job done (after a lot of problems, not all of it my fault) to reprogram the TPMS sensors on my C7's front wheels that triggered (no pun intended) this forum thread.
3. The range of TPMS sensors a particular TPMS tool can (re-)program varies ... don't assume that the shiny new tool you just purchased can program any random TPMS sensor. Note that most tools come with a time-limited or perhaps a lifetime software update that keeps the tool up-to-date re the vehicles and/or TPMS sensors it supports.
4. Using a tool that has an OBDII cable to read the car's existing stored TPMS sensor IDs is pretty quick work.
5. Whether a vehicle's TPMS sensors broadcast on 315MHz or 433MHz seems somewhat random, even within the same brand or even model (over the years).
6. I feel that at the prices that tire shops charge for aftermarket TPMS sensors, programming should always be free. In my case it was not (!), and I almost recovered the cost of the VT37 on just two TPMS sensor replacements (!).
7. Programming usually works better when you align the TPMS tool's transmitter through the tire's sidewall instead of directly at the sensor stem (where the signal has to pass more through the wheel body itself).
8. Always ask your tire/wheel shop for the make and model of the TPMS sensor(s) they just fitted to your vehicle.
9. If you vehicle auto-relearns wheel positions and new TPMS sensors (like the C7 does), then you pretty much can ignore dealing with TPMS issues (on that car). Just have the sensor replaced (with an OEM one, I presume that's all dealers will do) and you should be GTG for another 8-10 years on that wheel.
10. A TPMS tool (that can activate sensors and tell you the pressures) is kinda nice to use at the track, when checking tire pressures. I dunno what the typical accuracy of a TPMS sensor is, vs. a high-quality tire pressure gauge.

What I Do Not Know

1. Do OEM sensors come preprogrammed? I think so.
2. Does e.g. one OEM/GM/Schrader sensor work across the entire GM range? (That Amazon ad says ACDelco but you can actually see the Schrader text on the body of that TPMS sensor -- I have a dead one in front of me).
3. Do OEM sensors support both 315MHz and 433MHz for a given brand, and do they do that without special programming? Or do you have to at least program the OEM GM TPMS sensor for 315MHz or 433MHz, depending on what kind of Chevy its going into?
4. Do dealers exclusively use OEM sensors? And if so, do they ever program in new IDs?
5. What brands of aftermarket TPMS sensors have proven to have the best battery life?
6. Am I right in asserting that apart from the programming protocol, TPMS sensors are transmit-only?
7. Are OEM sensors just as (re)-programmable as aftermarket universal sensors? Or do they play some games where the vehicle protocol is non-changeable, but the frequency and/or IDs can be reprogrammed?

I hope this post helps others better understand TPMS if/when they're experiencing issues with their vehicle's TPMS system.

 

Well, the contrary to your reasonable post is that I can read what the TPMS sensor battery levels are, and while the LF one went from OK to LOW to (dead), and the RF I didn't check for a while, both rears are at OK right now. And I was wearing out rear tires much more quickly than fronts.

But yeah, the rears may die soon, we'll see.

 

If you can monitor it, fair enough. So you wear out rears more than fronts. But if you just swap tires, why are the rear ones at a different charge level than the front, assuming they are the OEM installed ones?

 

I have only replaced one sensor in the all the time that I have owned cars , and i have more than a few cars . My 2004 Expedition back in 2007 needed a single sensor . Here it is , 2023 and the other 3 are still orginal .... i have 3 other cars all varing in age and all have orginal sensors , who knows why one would go bad before the others ???

If it aIn't broke I don't fix it .....especially something that is non critical , gives a warning , is so easy and cheap to replace if it does go

Dave

 

How so? I have no idea about this since people have complained about how difficult it is to get someone to do it without damaging the wheels. Kinda why I thought that if you do one, do them all and be done with it since they are 10 years old. My other cars seem to have less concerns about the wheel being so low profile. Kinda dreading when I do tires.

 

I don't know about the GM sensors but I suspect that all OEMs go for the cheapest sensor they can procure. That would mean sensors that are preconfigured to the vehicle or set of vehicles they are going to be used on. That way there is no need to program at the assembly plant or in the field which avoids labor charges and could reduce equipment costs. At the plant, they might check the sensor's battery and broadcast capability and then slap the sensor on the wheel and slap a tire on the wheel or they forego the sensor check if the sensors come from their factory with few battery or broadcast issues.

One thing I do know is GM vehicle lines can use different sensors than other lines. For instance, I know the sensors used with our 2015 GMC Terrain are substantially different than the sensors in the 2015 Corvette. That may be because the Corvette sensors broadcast tire temps in addition to pressure readings to the car's systems. With the Terrain, the sensor valve stem can be replaced without replacing the sensor. With the Corvette the complete assembly is replaced.

Bill