Need help trouble shooting LTPWS light

[QB93Z]

I need help trouble shooting a LTPWS light. I started getting the Service LTPWS light on the Driver Information Center after I swapped the rear tires and tire pressure sensors to a new set of rear wheels. So, I suspect that one or both sensors was damaged during the swap.

This is for a 1993 ZR-1.

When ever I start the car, the LTPWS light is not on. After I drive about 3-4 miles, Service LTPWS lights up, and stays on.

I want to figure out which rear wheel has the bad sensor, but I can't get a code number.

I have tried to get a a code number using a Tech 1, but it reports no DTC even though the Service LTPWS light is on.

I have also used a scan tool (DataMaster), but it reports no codes as well.

Is there something special about the way the LTPWS faults are reported? The FSM says to read the codes to tell which wheel sensor is bad, but it isn't working for me.

Any ideas?
Thanks,
Jim

Possible dead receiver.

[QB93Z]

While this has been going on, I got a real Low Tire Pressure signal from a front tire. Is there one receiver for each wheel or one receiver for the car?

[White Bullet]

Originally Posted by QB93Z

While this has been going on, I got a real Low Tire Pressure signal from a front tire. Is there one receiver for each wheel or one receiver for the car?

I believe that there is only one receiver.

[GOLDCYLON]

One receiver per car or LTPWS module. 4 transmittors one per wheel. Just a guess but did they but the bands back on the right wheels or cross the pair?

[GrayZ]

Jim, do yourself a favor and take those puppies off and put em in a
pickle jar, as a conversation piece.

Heck, even i can tell if i got a flat tire.

[QB93Z]

I hear ya Keith! But, I am on a quest to figure this out. I guess I will start swapping wheels around to try to find the problem.

It just seems odd that the LTPWS light comes on but there is no code set.

Jim

[tomtom72]

I'm fairly sure that the 90 system and the 93 system have different tire sensors. Soooo I offer this as just a fwiw. My 90 does the same thing and as I have an extra set of tires & wheels(OEM ones) I changed out each wheel till I found a culprit. In my case it was my right front sensor, no code just the service LTPWS light exactly like you are seeing.

I did some reading over at the NetReg site in the How To section(?) under the maintenance tab. My conclusion is my issue is the battery, they are a fairaday type. It gets stuck, voltage not enough to power the sensor, sensor dropes out momentarily & lights the DIC light but sets no code because the battery starts working again almost instantly, sometimes. Stop car & shut down, restart and no light. Drive slowly for awhile and no light. Drive slowly to a highway and go fast and the light comes on. Drive fast long enough, with varying speeds and the light comes on and goes out sometimes. Drive a highway long enough with the light on and eventually it may go out, and after another while it may come back on.

Scott Fabre says that the battery gets stuck in it's track. This can be stuck like glued in place, or stuck momentarily. Either way, no voltage prodouced and a LTPWS service light. In my case I have three new sensors and had to cop a used right front....that's the one on my car that is the root of the my light(s). I took it apart before I installed same in new tires & wheels. I was doing Scott's test, shake it to see if you can hear the battery moving in it's track. Mine was intermittant in making sound, hence movement, hence voltage for the board to report in to the module. I think that the plastic rails(track) get worn & the battery gets cocked and stuck. JMHO on the diagnosis part. Sorry to be soooo long winded about this.


Tom

Link to page at NetReg site:
http://www.zr1netregistry.com/ZR1_howto.htm

[GOLDCYLON]

Tom your correct the 93 has the white bodied sensors with a somewhat pryamidish shape vs the 89-92 black bodied sensors which were rectangular. Different freqencies as well. While the pizzo unit is probably the culprit I still wonder if when the tires were swaped out if the sensors were put back onto the right rims? They are wheel specific (hence all those groovy, yellow, orange, green labels) so I wonder if thats whats going on here as well. Its also possible the units were damaged during the break down process by the tire shop.

[tomtom72]

Thanks for confirming the year break in the progression of the system, Daryl! I was aware of the fact of a break, I just couldn't remember when.

That's why I just tossed it out as a fwiw. The no DTC was what got my attention in this case as it's exactly like my symptoms. My diagnostics were easy as I have the OEM tires & wheels & sensors for my car still intact & I know that they worked (no lights on DIC). I do believe that if the "battery" gets stuck, it minicks a "intermittant fault" and doesn't set a hard code. I say that because the light goes out upon shut down & restart. Or in my case, it goes out if the "battery" decides to come back from coffee break!

My wear theory is bassed upon our "How To" section and the fact that my OEM stuff only had like 8k miles on it in almost 15 yrs. I bought three NOS sensors and the right front replacement was from a salvage yard with 40+k miles, or at least that's what they said........and that's the one with the worn battery track, and it's the one setting my service light.

I should look up the system in my 08 Cobalt's FSM and see what is different? I wonder if they changed the power supply???