gm tpms

gary__April 24, 2009

Purchased a set of wheels for a 2008 HHR. The sensors that came with the car are on a set of snow rims. I purchased a set of sensors from a junk yard to put in the new rims. The tire store guy says the sensors go with the car, so I'd have to take it to the dealership to have them match the frequencys of the different sensors to the system to get the dash light off. I'm NOT refering to the process to tell the system the orientation of the wheels on the car.

Here's the deal. Sometimes the system doesn't see any tire pressure from any wheel. Other times it see's anywhere from 1 to all four wheels. The dash light goes out when it's reading all four. Anyone know why it's doing that? Is there anyway I can tell the system that it's found the sensors when it's working so it will keep working? Almost seems like the system is hunting for them and randomly finds them. I really don't know anything about it though. The only info I've been able to find is about retraining the origninal sensors, not what to do when you replace them.


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Some models by design will accept the "new" sensors by default if the vehicle has been driven long enough. Chrysler's by design will do this. GM's normally will not. Each sensor has its own unique ID number that the car needs to know in order to accept the signal that the sensor sends out. Simply put, if the system just accepted any signal it receives, imagine what would happen every-time you got into traffic, and the car next to you was transmitting it had a low tire. (VBG)

So to program the car to accept the sensor ID's and the location of the sensors one way that "usually" works is start with the tires correctly inflated. Now turn the key on, and using a key fob hold both the lock and unlock buttons for about five seconds. The horn will beep. The system is now in training mode. Go to the left front tire and start letting air out until you hear the horn beep. This should take about 6 to 8 psi loss to do this. Now move to the right front, and repeat. Now go to the right rear and repeat. Then go to the left rear and repeat. The horn should beep twice indicating the system is trained. Now properly re inflate all four tires. You still may need to drive the car about five minutes and then using the in car driver information system (if equipped) verify that the car sees the sensors and that they are reporting.

Because many cars can use routines like this, very few shops have spent the money to have tools like the BARTEC 300+ or BARTEC 400, which make doing TPMS a lot more professional. These tools would allow the shop to test the sensors ability to receive command signals and then when the sensors transmit their data, receive that data and display it for the tech. One of the pieces of information would be the strength of each sensors internal battery.

Lastly, its not uncommon that we find certain aftermarket wheels simply interfere with the sensors radio signal and that causes the car to not consistently receive the signals. Without testing your car and looking at the sensor IDs stored in the on-board systems, and seeing the ID's of the sensors in the wheels there is little to no way of anyone progressing beyond this point reliably. Some models require an O.E. level scan tool to change the stored sensor ID's, or a shop can do it if they have a tool like the BARTEC 400. This does NOT have to go to a dealer, but I can tell you there is only ONE shop in my town other than the dealer that could work on this for you. Guess who that is.... VBG...

    Bookmark   April 25, 2009 at 9:07AM
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The process you mentioned are as stated in my owners manual. Hasn't worked for me. If I'm lucky, I'll try it again when it's already getting a reading on all four wheels and see what happens. The tire shop guys said something else is required when sensors are replaced and that another customer told them it cost him $100 and some to do at the dealership. Don't remember what kind of car it was but it wasn't a chev. The tire shop said they have a tool to tell the system which sensor is on which wheel which they use when they change tires, but it doesn't work if the sensors came off a different vehicle of the same make and model. What seems strange in my case is the system sometimes see's some or all of the sensors, sometimes none. Seems like it ought to do the same thing all the time.

I'd be happy to let you take a look at it...if you're shop is in Central Oregon :) Actually I'd be just as happy with the dash light removed or blacked out. Near worthless feature as far as I'm concerned. Surprised you sprang for the tool. Don't think I'd do it unless tires and wheels were my main business.

Thanks for the info.

    Bookmark   April 25, 2009 at 5:32PM
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Quote " I'd be happy to let you take a look at it...if you're shop is in Central Oregon :) Actually I'd be just as happy with the dash light removed or blacked out." Quote.

Disabling the system would in fact be illegal. The light coming on is the correct response for a system that is not capable of alerting the driver that one of the tires is incorrectly inflated. (all report under by 25% or more, some actually will report if over inflated too).

Quote. "Near worthless feature as far as I'm concerned." Quote

Remember Ford Explorers, and rollovers with Firestone tires? The actual cause of those accidents was driving with the tires under-inflated. This system is intended to reduce accidents and save lives.

Quote. " Surprised you sprang for the tool. Don't think I'd do it unless tires and wheels were my main business" Quote.

If I didn't buy the tools to do the job correctly, then I would not be living up to the promises that are made to the public that being a professional technician implies, as well as requires. What you SHOULD be questioning is why you have things done at a shop that didn't (doesn't) buy the correct tools to service your vehicle.

There is a difference between price and cost. You very likely have an independent technician near you that is already equipped and trained to solve this problem, except you choose to do business with a place that has not kept pace with today's technology. Your car may well need to have the sensor ID's manually programmed in. A shop with the Bartec 400 can do this, and a shop with a Tech II (GM factory) scan tool and the Bartec 300+ can also do this.

    Bookmark   April 26, 2009 at 1:30PM
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