View Full Version : Need help trouble shooting LTPWS light
QB93Z
02-23-2009, 07:21 PM
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
Jeffvette
02-23-2009, 07:49 PM
Possible dead receiver.
QB93Z
02-23-2009, 08:22 PM
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
02-23-2009, 09:25 PM
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
02-23-2009, 10:07 PM
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
02-23-2009, 10:39 PM
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.
:dontknow:
QB93Z
02-24-2009, 12:30 PM
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
02-25-2009, 08:26 AM
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. :redface:
:cheers:
Tom
Link to page at NetReg site:
http://www.zr1netregistry.com/ZR1_howto.htm
GOLDCYLON
02-25-2009, 08:38 AM
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
02-25-2009, 09:28 AM
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!:sign10:
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....:neutral:....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???:icon_scra
QB93Z
02-25-2009, 01:41 PM
Thanks for the discussion.
I have read the NetRegistry HowTo section and I agree with what you have posted. It is reassuring to hear that someone else has had the "momentary" fault that turns on the light but then goes away so there is no code number stored when you try to read the code. I thought I was using the Tech 1 wrong.
I will try swapping wheels around to see If I can figure out which wheel is the problem.
QUESTION: Will the wheels from my 1996CE have the correct sensors for the 1993?
Am I right in believing that if a wheel sensor had been permanently damaged during tire remove/install the LPTWS light would come on and there would be a code number set? Has anyone had that happen?
GOLDCYLON
02-25-2009, 01:47 PM
QUESTION: Will the wheels from my 1996CE have the correct sensors for the 1993?
Yes they are the same sensors
Am I right in believing that if a wheel sensor had been permanently damaged during tire remove/install the LPTWS light would come on and there would be a code number set? Has anyone had that happen?
Yes, which is why the lazy Piezo cell or the bands were put on the wrong wheel theory is holding. If it was "damaged" a code and the light should hold.
Make sure you clear everything out code wise before you put on the other set of wheels.
Jeffvette
02-25-2009, 02:31 PM
Yes, which is why the lazy Piezo cell or the bands were put on the wrong wheel theory is holding.
The units emit a radio frequency to the receiver. As long as the receiver gets that code, it does not care where that sensor is sitting. The reason they are color coded is they have a certain code tied to them. That code then signifies that the band now has an issue. So now that you know the band that is causing the issue you can go to the corresponding wheel, as long as they are installed in the correct location.
QB93Z
02-25-2009, 02:46 PM
Thanks for the clarification Jeff. It all makes sense to me now.
I guess the most direct way to find the "lazy" sensor will be to put the wheels on the 1996 one at a time and see which one causes similar symptoms.
GOLDCYLON
02-27-2009, 04:27 PM
Any updates? :dontknow:
Jagdpanzer
02-27-2009, 04:36 PM
Are the wheel sensors the same for all years?
If not, will earlier year sensors work on later year cars and will later year sensors with ealier year cars?
GOLDCYLON
02-27-2009, 04:55 PM
No they are different MY 89-92 used the Black bodied transmitters and MY 93-96 used the White bodied transmitters. Both had different frequencies so you cant mix and match. The bodies of the units are a different shape and the counterweight is different on the strap band as well.
However, has anybody actually really tried to see if a set of 4 newer transmitters will work on a older car or vice versa? Not that I have read about anyway in any forum. No matter what set of four transmitters are used they do transmit a frequency. I wonder if the older cars will read the newer car frequency and not error out? Good question, would be great if somebody had both and earlier and later car and could swap wheels for the good of the cause.
My guess is probably not as the LTPWS module are probably set to scan for only a certain frequency.
QB93Z
02-27-2009, 10:47 PM
No update. I have been busy with our business. I won't get a chance to swap wheels until next week. I will let you know.
Jim
vBulletin® v3.8.11, Copyright ©2000-2025, vBulletin Solutions Inc.