froggy47

Please no guesses, If you know please tell me how you know. It may be in the FSM. If you have a 2011/12/13 fsm and could take a pic with smart phone & post it that would be great. I'm making some pressure vessels with sensors & want to pressurize at the high end of acceptable, you know without tripping the nanny to depower the car.

Thanks.



Video will post if it works.

Bill Dearborn

Save your time the pressure vessel idea won't work. With the 4 sensors sitting at a constant pressure in a pressure vessel and stationary from a rotational stand point they will update the car once every 30 minutes. Once the car is moving and the tires rotating the sensors update once each 30 seconds. When 25 mph is reached sufficient centrifugal force is reached to make them start broadcasting at a 30 second interval. The 08 and earlier cars used different sensors and the system was programmed differently so thosee sensors only updated once per hour when stationary. My 08 would drive fine for up to a half hour and then the system would trigger a failure for all 4 sensors even though the car had been programmed to them. I would place the pressure vessel in the rear cubby. I suspect your 13 will be less receptive and will trigger in less than 30 minutes.

I have the 09 FSM and the TPMS works the same in it as it does in the 13. Here is the description of operation from the FSM:

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 minutes 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 J-46079 TPM special tool 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. For more information on other functions of the RCDLR, refer to Keyless Entry System Description and Operation .

Here are 4 DTCs that can be set if sensors don't broadcast within 18 minutes of the car achieving 25 mph.
DTC C0750, C0755, C0760, or C0765
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC C0750: Left Front Low Tire Pressure Sensor
DTC C0755: Right Front Low Tire Pressure Sensor
DTC C0760: Left Rear Low Tire Pressure Sensor
DTC C0765: Right Rear Low Tire Pressure Sensor

Circuit/System Description
The tire pressure monitor (TPM) system has a radio frequency (RF) transmitting pressure sensor in each wheel/tire assembly. As vehicle speed increases, centrifugal force closes the sensors internal roll switch, which puts the sensor into Rolling mode. The remote control door lock receiver (RCDLR) receives and translates the data contained in the tire pressure sensor RF transmissions into sensor presence, sensor mode, and tire pressure. Once vehicle speed is greater than 40km/h (25 mph), the RCDLR waits for the sensors to go into rolling mode. If one or more sensors do not go into rolling mode, or do not transmit at all, the RCDLR will set DTC C0750, C0755, C0760, or C0765 respectively.

Conditions for Running the DTC
Vehicle speed is greater than 40 km/h (25 mph).
Conditions for Setting the DTC
A sensor does not transmit for 18 minutes.

Action Taken When the DTC Sets
• The tire pressure monitor indicator icon on the instrument panel cluster (IPC) flashes for 1 minute and then remains illuminated after the ignition switch is cycled ON and the IPC bulb check is complete.
• If equipped, the driver information center (DIC) displays the suspect tire pressure as dashes.
• If equipped, the DIC displays a service tire monitor type message.

Bill

froggy47

Thanks Bill, I did not know centrifugal force was required, I was hoping it was "just motion". Anyway they are built & correct (I hope) sensors installed so I'll try them when the stock wheels come off for this weekend. If you are right, they will program ok, but fault when vehicle speed call for rolling mode. Shall see. I made 4 - one for each corner.



Worst case I'll take them out & put into the wheels.

I wonder if there is a way to hack the sensor into thinking it is rolling all the time?

Most of the info I could google is way too basic, no engineering details.

froggy47

Bill, anyone, given that I have these pressure vessels with sensors & correct pressures.

Is there a way to arrive at the track/autox and reset/initialize everything and get XXX # of minutes of full engine performance, get my abs back working (see other thread) but probably still have tc/ah offline. That might not be too bad.

I will try Sunday. I will already have the sensors paired (as Bill states the pairing should be remembered). Then disc. battery. Then reconnect battery and reconnect swps and see what goes.

I have been in touch with a mfg (UK) who is working on a tpms disable/bypass for GM. They already sell one for Ford, black box that just sits in the car, you press one button to train/pair the 4 sensors & done. Under $100.

Will post if/when I get one.

c5racr1

96GS#007

Other than as an engineering exercise, far easier to just mount them in the wheels. It’s not like they’re so heavy they have any impact on performance, they’re not like the old band mounted sensors that could break free, I can’t recall the last time I heard of a tire shop breaking one during dismount/mounting of tires, it’s less stuff to carry around.

froggy47

Costs over $400.



I can buy a tire with that.

froggy47

Not going well, I put the pressure vessels (pv) in the car and surprisingly all the pv values showed on the dic. Drove to get 10 mi to get gas and on restart the tpms started & then proceeded with low power limp mode. Got home & disc batt for 5 min reconnect & drove and now ck eng is flashing & limp mode. Disc. swps which worked before (with loss of abs) and that did not work.

Maybe no race tomorrow if I can't fix it.

CRAP.

c5racr1

froggy47

Probably, but I like a challenge.

Maybe a Tech 2 can turn it off, always wanted one & I'm on my 3rd Vette.

c5racr1

froggy47

Ei, yi, yi

froggy47

LS1 edit?

froggy47

Connected all back up with sensors in original tires, going for a ride to see if ck eng light & rough running clear.



No dice, still have service trac control
service active handling
ck engine icon
skid car icon.
rough running
Parking it until I get the tech2 next week.

I would have thought connecting everything back up would have done "something"

Bill Dearborn

Not understanding why disconnecting the steering sensor killed your ABS. When I read the FSM it clearly states if the SWPS signal is missing it will shut down Stability Control. However it doesn't say anything about shutting down ABS or TC. My 08 with the old EBCM didn't shut down ABS/TC when the connector was pulled, however, there was one difference in the Action Taken section of the associated DTCs, they also mentioned ABS and TC remained functional while the newer FSM is mum.

Now if the yaw sensor is disconnected then ABS shuts down. The schematics show the yaw sensor and steering sensor bidirectional data lines are spliced together but I can't find the connector where that happens as there seems to be a printing error in the manual.
Bill

froggy47

Don't know as much as you, Bill, but 100% on my 2013z it kills abs.

Any help what I should do to get the car back to sq one when I get the tech2 I'll have a learning curve with that.

c5racr1

c5racr1

Bill Dearborn

Pull the battery ground cable and leave disconnected for 1 minute. Then before reconnecting the cable touch it to the positive cable and hold it for a few seconds. This should discharge any charges that have been stored in the electronics. Then reconnect the cable and drive the car to see what happens.

When you pulled the steering sensor connector under the dash and the ABS failed did you get DTC C0252?

Bill

froggy47

Thanks guys, I was also thinking that next. Force the module to reread/reregister/etc.

You guys are great.