TPMS: How Does It Work? ...and why it is good to know?

[mrrsm]

While investigating CHEAP but PRACTICAL TOOLS for use with either PICO-Scope or Hantek Oscilloscope, I ran across this YT Video that covers the topic of Tire Pressuring Monitoring Systems (TPMS from A to Z) with some very surprising discoveries... and access to more FREE Wireless Investigation APPS that will probably pique the interest of @TJBaker57 in particular:

Measuring Pressure Remotely:

URH Universal Radio Hacker:

https://github.com/jopohl/urh

 

[rchalmers3]

Allow me to piggyback on MRRSM's most recent post regarding TPMS and Trailblazers.

I don't have precise diagnosis details, but I'll share an experience that may help others reading this thread.

My Trailblazer started losing signal to a single TP sensor. It was intermittent and the pressure reading went from correct to zero and back to the correct PSI over the course of a days driving.

I'm a simple minded fellow and ASSUMED the issue was a failing sensor in that wheel. It was only affecting that individual wheel, so what else could it be, right? Wrong.

After purchasing a package of 4 tire pressure sensors and the learning tool off of Amazon, I had the sensors fitted at a tire store where they attempted to program them. However, after fitting those new sensors, there were now 2 sensors that would not communicate or program correctly.

The folks at the tire store warned me beforehand that the issue I was describing could be a communication issue between the car and the wheel sensors, not necessarily a failed TP sensor. Turns out they were right.

I replaced the Liftgate Module and was able to program all four TP sensors immediately. The liftgate module is the receiver for the TPMS and apparently can lose reception over the years. I happened to have a spare parts car in my yard for parts robbing, so the cost to me for the liftgate module was zero. The Chinese sensors, formatting tool and sensor installation at the tire store cost me $110. Maybe I didn't need them, that is the point I'm sharing with you in relating my story.

Rick

 

[mrrsm]

Rick... Just to clarify the differences between the Black Plastic LGM mounted in the center of the Rear Lift Gate and THIS Lower Rear Lift Gate Locking Control Solenoid Mechanism... THIS is NOT the item you replaced as the LGM Radio Transciever... correct?

 

[rchalmers3]

I replaced the module, not any of the latch pieces.

The FSM has a good description of the LGM housing the radio frequency receiver and how it communicates with the BCM, but I skipped over the testing and diagnosis of the receiver because it took me all of 5 minutes to pull out a spare one and swap it in.

My intention of relating this experience is to caution folks to take it slow and read up on TPMS issues before pulling the trigger on the parts shotgun.

Rick

 

[mrrsm]

Okay... So the only other issue to settle and clarify on this repair is whether or not using a Tech 2 is necessary whenever installing Brand New Lift Gate Module...

 

[rchalmers3]

Nope, it's plug and play, according to the FSM and my experience.

Rick

 

[vipergg]

I had an issue where they replaced all 4 sensors and the TPMS light would keep coming on no matter what they did . They relearned the sensors and I would drive a ways and the light would come back on and they couldnt figure it out . I finally took it home and did a little reading and what I did was pull the fuses for the LGM and left it out for 30 minutes and reinserted it . Never had another issue , so who knows with this system . In my case a simple reboot appeared to fix the problem . So my first advice would be to just try and reset the LGM by pulling the fuse if you are having problems .

 

[Mooseman]

I'm actually jealous of my son's VW Passat. It has no TPMS sensors. It determines a low tire by the ABS wheel speed sensors. It's resettable from the DIC if you replace the tires. Doesn't tell you actual pressures though but it's still better than the flashing light just telling you to check the tires if you don't have a DIC. And no need to buy extra sensors for your winter tires.