First post LTPWS mystery

[Ron Ashcraft]

This is a test for for all of you Techies out there and a test for the "Forum". I will make this same post on the Net and compare responses.
LTPWS worked fine for 11 years. Now it works normally until the car makes a right Ninety Degree turn to the Right. Then the LTPWS light comes on and stays on until shutdown.
Any theories?

[Z Factor]

This is a test for for all of you Techies out there and a test for the "Forum". I will make this same post on the Net and compare responses.
LTPWS worked fine for 11 years. Now it works normally until the car makes a right Ninety Degree turn to the Right. Then the LTPWS light comes on and stays on until shutdown.
Any theories?

I don't have a theory about your mechanical problem since I've never had that happen, but I do have a prediction regarding the responses. I suspect that it will take longer to get answers/opinions here on the forum since we are still new to many people. While we have some gearheads that can solve any problem, they only pop in every once in a while because the forum is still getting it's feet wet. So even if you do not get a response right away, don't give up on the forum just yet. I have been noticing much more activity recently, so that should change in the near future.

:cheers:

[Tyler Townsley]

This is a test for for all of you Techies out there and a test for the "Forum". I will make this same post on the Net and compare responses.
LTPWS worked fine for 11 years. Now it works normally until the car makes a right Ninety Degree turn to the Right. Then the LTPWS light comes on and stays on until shutdown.
Any theories?

It does not like cold country and is tired of being in hibernation for 6 months at a time. You need a 160 deg thermo to take care of the problem. HaHaaaa

Sounds like one of the straps is broke or loose.

Tyler

[bigd]

I also have an intermitent LTPWS problem. The warning light comes on whenever it feels like it. I've noticed no pattern. The sensors are being removed at next tire change.

[WB9MCW]

Here are the details from the zr-1 net/regis. on the system

9. TITLE - Low Tire Pressure sending units



YEAR(S) - '90-'91



PROBLEM - Low Tire pressure sending units are known to go bad. Specially in earlier ZR-1's. If you see your LTPWS light come on then most likely you have a bad Low Tire pressure sensor in one of your wheels



CORRECTION - Follow the GM service manual to find and replace the bad sensor.



SERVICE BULLETIN/RECALL - 90-340-3E and 90-389-3E




27. TITLE - Possible problems with high speed driving and LTPWS sensors.



YEAR(S) - All



PROBLEM - LTPWS sensors in high speed running can brake loose and cause your tire to become unbalance or unstable. The LTPWS sensor plastic case is simply attached to the stainless strapping band with plastic tangs and is no way up to the centrifugal forces that ultimately come into play at high speeds. Merely the act of breaking loose inside a mounted wheel and tire assembly at high speed can cause further damage, potential quite serious, to the tire casing.



CORRECTION - If you are going to do a lot of high speed driving like in the Pony Express 100, you should remove the sensor from each of the tires.



Thanks to Dennis Duchmann for this information.


Included in the "ZR1" RPO (Regular Production Option) is the Low Tire Pressure Warning System or "LTPWS". One of the most common lights illuminating in the Driver's Information Center (DIC) is the nuisance "LTPWS" light. These can be caused by several reasons including a fault in the system or other radio frequency interference, even driving next to another LTPWS equipped Corvette. Let's explain the operation of the system.



A transmitting sensor is installed (by large band type clamp) on each wheel. Each sensor has a separate identification color and frequency which is transmitted as the wheel moves. The movement of the wheel provides the electric power necessary to power the transmitter, therefore, no battery is necessary. This "Piezo-Electric" energy develops after only 30 seconds of operation at over 25mph.
A receiver module is located within the dash which receives the signal transmitted by each sensor. When the tire pressure is low (below 25psi), the sensor is triggered causing it to stop transmitting. The receiver recognizes the absence and turns on the warning indicator "Low Tire Pressure". If the receiver unit senses any other malfunction in the system such as a sensor that doesn't "report in", then the "Service LTPWS" light illuminates.



"Service LTPWS" usually indicates a faulty sensor and a code will be stored within the receiver module. The '91-'95 model ZR1's have the ability to be diagnosed and codes cleared through the Tech 1 hand held diagnostic tool, and by the Assembly Line Data Link or ALDL connector. The '90 models do not have this capability. In fact, the '90's diagnostic procedure can be extremely time consuming and basically requires replacing each wheel separately and then road testing until the faulty sensor is located. This can be done with another non-LTPWS equipped wheel or the vehicle spare. Start by replacing one wheel/tire combination and then driving the vehicle. Wait for the "Low Tire Pressure" light to illuminate (ignore the "Service LTPWS" as it will stay on). When the replacement unit does NOT set off the "Low Tire Pressure" light, then you have located the faulty sensor. In all cases, after repairs are made the code(s) must be cleared manually from the receiver. They will not clear themselves.



Important Note #1: Because new sensors cost $150 each, and to avoid unnecessary damage, BE SURE to alert the technician that your wheels contain the LTPWS sensor prior to performing any tire repairs or replacements. The sensor is originally placed 180 degrees from the valve stem, usually marked by an exterior decal.



Important Note #2: There are numerous errors in the service manuals regarding the correct color locations and part numbers for the '90-'92 MY (Model Year) sensors. The correct information is below. Keep it for future reference.



GM #10098494, Right Front-Blue
#10098495, Left Front-Green



HOPE THIS HELPS :thumbsup: :thumbsup: :thumbsup:

[HHZR1]

I would guess that one of the sensors is getting tired. I have heard that the capacitor that stores the piezoelectric energy goes bad. In an early car, the problem is that you don't know which sensor is the weak one since the receiver does not send out a different error code for each wheel. In my case it was two real bad ones and one boarderline one. I borrowed a box from Gordon Killebrew (Gordon's School in Tennessee. The best money I ever spent!). It had a receiver from a newer ZR1 and would put out a different code for each wheel sensor failure. I drove around with it until it gave an error and then I could determine which was the bad sensor(s).

You might also try simply reducing the pressure to 20 psi in one wheel at a time and driving around. It should take a block or less to light the Low Tire Pressure light. Ignore the Service LTPWS light if it comes on. If you are lucky, one tire will respond a lot slower or not at all. If so, you should replace that one.

I still need a RF sensor. It works ok when I drop the pressure but lights the Service LTPWS light on occasion. I tried twice to order a new one from www.gmpartsdirect.com ($140 versus $200 from GM) but it comes up as "out of stock". I also tried Corvette Central and my local Chevy dealer with the same answer. I'll try again later and hopefully succeed.

In the worst case, it is easy enough to remove the bulb in the dash for the Service LTPWS light.

Good luck.