Hey guys,

how can I test my TPS sensors before I install in my wheels? The reason I am asking is that a 3 out of 4 of my new pressure sensors are bad and now I have to take my brand new tires/rims to the tire shop and have them do this again. It sure would be nice to somehow test the sensors before install. The problem with the sensors is that they read too high (~10psi). There were no issues in teaching the locations or anything like that and they do communicate with the receiver just fine. I called the service dept at Russ Chev here in Oregon and they said that there was no calibration for the sensors. They either work or they dont work given that the teach process was successful. An additional note on sensors for C5's is that GM's supplier has recently changed so I was told. Apparently they now use the same supplier that currently builds the C6 style sensors. Makes me wonder how reliable this new sensor is. I will keep you posted after my new sensors are in.

any comments?

 

I don't think your new sensors are bad. I could see one going bad but not 3 brand new sensors. Have you put a few miles on the car yet. It takes a while before the sensors work properly. After they are trained they usually are recognized right away but they don't seem to be correct until you have driven the car for a few miles.

 

yep put on over 130mi since installing.

They communicate with the receiver just fine where they slightly increase in pressure about 3psi while driving it. I agree this is an interesting situation and unlikely as it sounds I have 3 bad sensors. I would love if for some miracle that the sensors started reading correctly but at this point that doesn't seem likely. I would just install my old sensors becasue they worked fine but they are near end of life @10yrs old. Maybe the new supplier makes bogus sensors? who knows we dont have the history to support the sensors where this is a recent change.

 

Every tire no matter what car or truck its on will increase the internal air pressure when the air inside heats up. Thats simple science (gases expand when they get warm), Mine heat up 3 lbs normally I have seen them gain 4 lbs on a cold morning (30 degrees) that warmed up to the 80's (I was driving from Michigan to Fl. in the winter).

There are tools that will test the TPMS. They test for battery strength, frequency that they transmit, they will give you the individual serial number of the sensor, They will give you a pressure reading, I have this model. http://www.otctpms.com/products/general.php

Most tire shops have these as the newer GM sensor (for the C6 etc.) you need this tool to train the sensors, a magnet doesn't work. But even with this tool there is no way to test the accuracy of the sensor. (but I've never heard of this being a problem)

If they aren't correct I would take them back to who ever I bought them from, but this means you need to remove them from the wheels and thats such a pain, and you would need something to replace them with or you would get error codes on the DIC.

 

yep you're right about the gas in the tire expanding and I completely comprehend that. I'm an engineer. simply stated PV=NRT. that's an equation all engineers are familiar with believe me. The reason I stated that the pressure increases while I drive is the fact that the sensors are obviously talking with the receiver and nothing more.

Let me clear something up about the C5/C6 sensor issue. It's been a very trying week for me and I must be getting tired. Sorry. The C5 and C6 sensors are different animals. You cant use a C6 sensor in a C5 and expect it to work and I understand that. I was told that GM has been using two different suppliers for sensors (1 for C5 style and 1 for C6). Apparently, GM has now opted to go with one supplier (the one that makes the C6 sensors) for both sensor types (C5/C6). The design is not the same obviously. It is possible for one supplier to make two completely different design sensors. We do this all the time in my line of work.

 

How did you make out? I just replaced a bad TPMS sensor on my C5 and the new sensor reads 8 psi high.

 

How many miles have you driven the car since you put in the new tpms sensor?

 

You could have some fun and experiment with one, tape one to the outside of your tire and program it. Then go for a ride around the block to activate it. It should read 0 PSI I'd imagine... if it reads 8 or 10 then it's "off"...

I can read the headlines now, "Elderly Lady Crossing the Street struck by a TPS, Law Suite Pending"....

 

Are you sure it is not your tire gauge that is 10 lbs off ????

 

Good question. I don't trust the old pencil gauges. I suggest using the new digital tire gauge....maybe two of them, just to double check the accuracy of the readings.

 

The most mine are off is 2-3 pounds.

 

Less than a mile, just enough to wake up the sensors and get a reading on the DIC.

 

The other three wheels read within 1 pound of my tire gauge.

I replaced the sensor on the fourth wheel because the TPMS was getting no reading (the DIC would show pressure on this wheel as XXX), and the system refused to "learn" this wheel when I followed the TPMS calibration process. Not surprised, as these are 10 year old wheels.

The new sensor is an AC Delco unit purchased from one of the bigger Corvette supply houses.

 

Interesting suggestion!

When the new sensor arrived, I wanted to check if it was operable. I ran through the TPMS calibration procedure holding the new sensor in my hand near the correct wheel position, but the TPMS would not "learn" this sensor. The TPMS learns the new sensor now that it's mounted on a wheel.

After a close look at the sensor, I speculated that it's intended to be inoperative when off the wheel, as there is a small hole with an electrical contact that I suspect is engaged when the sensor is mounted on the rim, closing the circuit through the rim back to the metal valve stem. There is no other "on/off" switch I could find, and one would think the manufacturer wouldn't want the sensor to be active and draining the battery while the part is sitting on a shelf somewhere.

This is speculation, because I had a local repair shop install the new sensor on the wheel and I didn't get a chance to examine the rim and see if my hypothesis is correct.

Anybody have a bare rim and sensor they can look at to confirm?

 

Thats not enough, put some more miles on. I've had them take as long as 20 minutes of driving before they become accurate.

They will work without being mounted in a wheel. I just put new wheels on last month (for the 3rd time in the last 3 years), and I bought new sensors. I trained them from the drivers seat without ever getting out of the car and labeled them with a piece of masking tape as far as the location and put them in a box, just before I left for the tire store.

When I drove the car home the sensors were working in the correct locations, but it took a while before the readings were correct.

If you do a search you will find that quite a few other members have trained their sensors before they put them in the wheels.

 

Well, no joy so far. Drove about 50-60 miles this evening, cumulative about 1+ hour of driving time. The new sensor is still reading 8 or 9 psi high. I see its reported pressure increase and decrease about 3 psi as the tires heat up and cool down, right in line with the other three wheels.

 

Just an update on the sensor issue I had a few weeks back. I'm sorry, I should have posted when the issue was finally resolved.

My isssue was that 3 of 4 new TPS sensors read too high (~10psi too high). I tried re-teaching the sensors several times and even replaced the air in the tire thinking that going from no pressure to ~30psi would somehow fix it. I drove the car for over 75mi but still the 3 sensors read too high. I heard from several people that driving it would help to stabilize the pressure. This was true for the one sensor that was working from the beginning where this one working sensor did settle from about 31 psi to 30 psi like my handheld gauge was reading. The other sensors still read too high. I went back and forth with the company that I bought them from but finally they agreed to send me three new sensors. These three new sensors were installed and worked AWESOME immmediately upon install and have been working great ever since.

Apparently, GM has recently changed vendors that make the sensors where this is what I was told by the company I bought them from. See my earlier posts for more info. Maybe there are some quality control issues with these new sensors I don't know.

 

Thanks for the info (and the suggestions, everyone)! I drove the car an additional 300 miles or so, and the errant sensor was still off, reading about 9 psi high. Just high enough that when the tires heat up the DIC would warn me of high tire pressure (wandering up and down past the 42 psi trip point according to driving condition made this a PIA)

Bottom line, I went to the local Chevy dealer and had them replace the sensor with a new one and the problem is corrected. All wheels now read 30-31 psi cold against pencil guage reading of 30 psi. I bought the first replacement sensor online for $159 and the supplier will refund this as defective merchandise. The sensor from dealer was $139 (yes, cheaper!), but there's a story to go along with this.

When I brought the car in, I told the service advisor my story and asked them to replace the sensor (they had nothing to do with the issue so far). He hesitated and darkly warned that it may really be a computer problem that they would have diagnose. I asked him to swap out the sensor and go from there.

After three frantic cell phone messages from the service advisor that they couldn't find the locking lug nut key, I called him back and said it's in the storage well GM designed into the left hand storage bin in the rear hatch compartment.

Couple of hours later, I get message that car was done and could be picked up. When I arrived to pick up the car, I asked the service advisor if they had checked that the TPMS system was now reading properly. He said, "yup, ready to go." I paid the bill and left, soon noting that the DIC was reading "XXX" for pressure on the wheel with the new sensor. That means the TPMS is not picking a signal.

So I went right back to the dealer, told the advisor there was a problem, and he got back on the "it must be a computer problem" hobby horse. I asked if they calibrated the TPMS; he didn't answer but pulled the car into the garage and asked a mechanic to recalibrate the system.

Over the course of 30 minutes, I watched a gang of four mechanics plus an assistant service manager gather around the car, trying to recalibrate the TPMS. They alternated between using the handheld RF reader and the Tech II diagnostic code reader to recalibrate. Finally, the service advisor emerged and said that the system was being finicky. I asked if they had tried using a magnet. A dim light went on, and the service advisor talked to one of the mechanics, who left and came back with a magnetized part retrieval tool (the kind at the end of a telescoping wand). They tried to recalibrate the sensors, and got three to take after 15-20 seconds of waving the magnet around; they couldn't get the new sensor to calibrate.

Service advisor reappears, and now he's sure there's a computer problem just aching to be diagnosed. I told him DIC had been working fine, problem started two weeks earlier when I switched to another set of rims. Problem was one sensor was dead, and when it was replaced, read 8 psi high. The dealer's sensor appeared to be dead (I didn't offer my opinion that their magnet was too weak and that's why it was taking so long to recalibrate the other three wheels)... so why not order me a new sensor and try again? He grudgingly agreed (after the service manager subtly nodded his head in agreement to my suggestion).

I left the dealer, went to AC Moore craft store, bought $3.49 worth of ceramic magnets, and recalibrated all 4 pressure sensors about as quickly as I could move around the car (about 5 seconds of magnet time per wheel).

I couldn't resist going back to the dealer, magnets in hand. Everyone except assistant service manager had gone home. I handed him my mangnets, politely told him the story, and pleasantly said they could keep my magnets as my gift. He said he had been watching all this unfold, but didn't intervene. He was highly sympathetic, said he had been service manager himself at another dealership that closed, agreed that this was not a good showing, wanted to see I was treated right, would get service manager to call me and would try to see if he could get me some sort of courtesy adjustment like discount on next oil change. He said this dealership really tries to do the right thing, they want only highest possible ratings on customer sat surveys and will do what it takes to earn it, that GM really takes them to task on less than perfect scores.

A week later, I'm still waiting for my phone call... or my survey

 

There is a new cover sheet on the TPS reports you know...

 

I don't understand this comment... please explain. Thanks!