TPMS woes

[leadfart]

That was not my experience. When one of my TPMS's went bad, my former dealership located the bad TPMS, when I got home, I put my spare on, reset the system, with my tool, and the code reset. I then took my tire with the bad TPS to Discount Tire, installed a new TPMS in it, put it back on the car at a later date, reset the system again, and have had no issues since then.

I also reset the system, when I change out to my DR's, to go to the track.

[leadfart]

I guess I'm confused? If Discount Tire located the bad TPMS, they could have replaced it, and done a reset, and you would be off and running. No Tech 2 needed, or am I missing something here? I don't "splain" things as good as Bill.

[9C1fanatic]

Our driving instructors have played with this quite a bit.

On the 2014 Caprice, the door label says 39 PSI front and 44 psi rear. After making many adjustments and hundreds of laps they confirmed that the best handling (best lap times) comes with using the factory specs. Using the Goodyear RSA tires, no data yet on other tires. Keep in mind this is also on a fully equipped and loaded police car. These cars have really good front to rear weight distribution. Adding the police gear tends to add more weight to the rear than the front which probably explains the big difference in tire pressure recommendations.

[storm9c1]

Our driving instructors have played with this quite a bit.

On the 2014 Caprice, the door label says 39 PSI front and 44 psi rear. After making many adjustments and hundreds of laps they confirmed that the best handling (best lap times) comes with using the factory specs. Using the Goodyear RSA tires, no data yet on other tires. Keep in mind this is also on a fully equipped and loaded police car. These cars have really good front to rear weight distribution. Adding the police gear tends to add more weight to the rear than the front which probably explains the big difference in tire pressure recommendations.

Hmmm...39 and 44psi may be great for the track or pursuit driving, but it's too harsh for everyday driving IMHO. Highway driving is especially annoying; every crack or concrete transition makes the tires ring like flicking a balloon with your finger. Therefore I keep mine at 35-37psi which seems to be a good compromise for civilian use. I have no "police equipment" and I bet very few of us do here, to weigh down the rear. The car handles just fine at 35psi, even at highway speeds. Yes, MPG does suffer slightly, but that is understandable. While the PPV handles WAY better than any of my B-Body Caprices, I am also used to smoother ride that large sidewalls and a BOF car provides. If I really wanted a harsh, noisy ride, I'd drive just about any other mediocre FWD strut car made today.

[9C1fanatic]

Me personally I prefer the crisp and stiff ride even for everyday driving but I totally agree that there is no substitution for the way a BOF vehicle rides, even a firmly sprung one. That is why Ill never get rid of my B Body.

[elc32955]

That's interesting on the pressures. There's a call-out in the 2011 PPV owner's manual that states the following (page 10-53):

When not driving at continuous high speeds or with up to three occupants and 45 kg (100 lbs) of cargo, adjust the front
and rear cold tire inflation pressure to 36 psi (250 kPa). See Vehicle Load Limits on page 9‑12 and Tire Pressure on page 10‑53.

Garner, did your group try the 36 PSI test and evaluate performance with an unmarked, or did you just check with a marked unit? I've been running 36 PSI cold based on this manual instruction.

On the TPMS, I know the folks at Discount did try a reset and were unable to. But this is the first time I've seen one of these sensors go wonky high and low on the pressure readings so I wasn't sure what to make of it. One specific reason for going to the dealer is that I was going to have the alarm setpoints lowered for the alarm threshold so on pretty cold mornings that I'm running 36 PSI filled cold at 80F and the pressure in the tires goes down to 33-34 since you've got a 50-60 degree temp differential (30F or thereabouts), the alarm doesn't start flashing and bonging because you just went below 35 PSI - my car starts alarming at 34 PSI usually. That fix takes a Tech 2 to make the programming happen. And, again that programming change is based on the 36 PSI callout in the manual.

[9C1fanatic]

Sorry unfortunately we did not test any unmarked units as all of the caprices in our fleet are marked and fully equipped. That is very interesting though I don't remember seeing that in the 2014 owners manual but I could've missed it.

[elc32955]

I just checked and it's not in the 2014 owners guide. Wonder why GM removed the flag note on the pressures.... I'm guessing maybe because there's no longer a 9C3 and all of the cars are now sold exclusively for patrol duty (I.E. marked units). But it's just a guess at best....

Eric

[ImpalaPPV]

Is it possible to just disable or have someone disable or adjust the settings for TPMS? I'm assuming it can't be done with a regular tuner and a dealer won't do it for liability reasons.

[smwalker]

Having some issues with My TPMS and just thought I would post what the service manual had to say about it for future use. Hopefully the 6 pounds of pressure added will fix my situation. But we are coming up on battery failure time even though the service manual says a lifespan of 10 years:

Tire Pressure Monitor Description and Operation

The tire pressure monitor (TPM) system warns the driver when a significant loss, or gain of tire pressure occurs in any of the 4 tires and allows the driver to display the individual tire pressures and their locations on the driver information center (DIC).

The system uses the body control module (BCM), driver information center (DIC), instrument panel cluster (IPC), remote control door lock receiver (RCDLR), a radio frequency (RF) transmitting pressure sensor in each wheel/tire assembly, and the serial data circuit to perform the system functions. Each sensor has an internal power supply with a 10 year service life.

When the vehicle is stationary, the sensors internal accelerometer is inactive, which puts the sensors into a stationary state. In this state the sensors sample tire pressure once every 30 seconds and do not transmit at all if the tire pressure does not change. As vehicle speed increases, centrifugal force activates the sensors internal accelerometer causing the sensors to go into rolling mode. In this mode, the sensors sample tire pressure once every 30 seconds and transmit in rolling mode once every 60 seconds. The RCDLR receives and translates the data contained in each sensors RF transmission into sensor presence, sensor mode, and tire pressure. The RCDLR sends the tire pressure and tire location data to the DIC via the serial data circuit where they are displayed.

The sensors continuously compare their last pressure sample to their current pressure sample and will transmit in re-measure mode if a 8.3 kPa (1.2 psi) change in tire pressure has been detected in either a stationary or rolling state. When the TPM system detects a significant loss, or gain of tire pressure, the tire pressure monitor indicator icon is illuminated on the IPC and if equipped, a check tire pressure type message is displayed on the DIC. Both the indicator icon and DIC message can be cleared by adjusting the tire pressures to the recommended kPa/psi and driving the vehicle above 40 km/h (25 mph) for at least 2 minutes.

If power is disconnected from the RCDLR or if the vehicle battery is disconnected each TPM sensor ID is retained but all of the tire pressure information is lost. Under these circumstances the RCDLR cannot assume that the tire pressures were maintained over an unknown period of time. If equipped, the DIC will display all dashes and the scan tool will indicate a default tire pressure value of 1020 kPa (148 psi) for each tire. Driving the vehicle above 40 km/h (25 mph) for at least 2 minutes will activate the sensors causing the DIC to display the current tire pressures. The EL-46079/J-46079 TPM special tool or the pressure increase/decrease method may also be used to activate the sensors as well.

The RCDLR has the ability to detect malfunctions within the TPM system. In the event a DTC is set, the tire pressure monitor indicator icon on the IPC will flash for 1 minute and then remain illuminated after the ignition is turned ON and the IPC bulb check has been completed. Any malfunction detected will cause the DIC to display a service tire monitor system type message