Thread: TPMS Puzzlement

My TPMS idiot light goes on and off. At first, I thought Firestone put on bad sensors, or didn't change them. But when it goes out, I get readings from all four tires. When it goes on, I either get one reading or zero.

Is it possible this is the module in the car malfunctioning? If so, where is it located?

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for curiosity's sake, have you checked for fault codes in the TPMS or ABS modules? If they're there it might lead you in the right direction.

Above, I asked where the TPMS module is, and never got an answer. Can you help me?

Hello?

Above, I asked if you had done the first step of diagnosing a problem on a modern vehicle. This has not been answered.

It's not the most encouraging when you offer help to someone and the response is 'i know more than you'.

But, to answer your question, there's not one.

04-06 cars have indirect TPMS, and do not have a dedicated module. It uses the EBCM and ABS modules and determines tire pressure variances by wheel speed. In these, different tire sizes, and levels of wear CAN effect TPMS operation. It also could be related to any TCS or ABS issues.

07-08 uses a combined effort of the sensors in the wheels, RCDLR (door lock receiver), DIC, and IPC to monitor the actual pressure inside the tire. Didn't you just replace the DIC? Hm.

In either system, you need to pull codes.

In your post, you asked, and I quote, "have you checked for fault codes in the TPMS or ABS modules?" Now, you tell me there IS no TPMS module. I'm confused....

How do I pull codes that clearly aren't OBDII codes, especially if the codes could be coming from seven different places? That's really what I've been asking all along.

You check for them the same way you do generic OBD codes, but it requires a more advanced scan tool.

Typically your generic OBD codes are stored in the PCM/TCM. With very few exceptions, almost every dedicated module, or CAN/LIN network module has the ability to store it's own fault codes.

I'm generalizing right now, because I don't have schematics for your car in front of me. This is also why I mentioned a dedicated TPMS module earlier, because I assumed you weren't asking for something that doesn't exist. My mistake. Finding what I posted earlier took a total of 3 minutes on Google to find.

Your generic $18 hand held scan tool won't give you the codes you're looking for. Harbor Freight will sell one that can get them cheaper than most other places, but it's still around $100 for an entry level tool, and they can range over $5k for a name brand tool.

There's also the option to drop the cash and have a shop check it out for you. Most will charge one hour's labor (typically $60-$90, and up) to diagnose the issue, and then you can fix it if you decide to.

In all honesty, all of this is readily available information that can be found within a reasonable amount time of searching online. I can offer help if provided with fault codes, otherwise I won't be replying again.

Above post is correct. Those codes will be stored using the OBD port on the vehicle, but your standard in store code readers will not be able to access systems other that engine DTC's. Your best bet is to go to a shop and have them pull the codes for you, as you are looking at anywhere from $100 and up for your own tool to do this. If you would like to look into investing in a tool, there are several options and I can help steer you in the right direction of what scan tool you will need. The one I use, and LOVE is the Autel Maxisys MS906 TS. But you're looking at $1800 that one, and if you aren't working on a ton of vehicles, it's a waste of money. You would be more inclined picking up a LAUNCH CRP129E for $250. As far as cheaper options, I am not sure how well some of the cheaper options that claim they can get into ABS, TPMS fair.

Got a $40 code reader. (Spending more than an hour of labor makes no sense.) It was a dead sensor on the right front tire, which makes absolutely no sense, as when the error light wasn't on, I got readings from all four tires. Nevertheless, after replacing the sensor, the light has not returned.

Is it possible the relearn wasn't done when I got the tires put on the car, and that somehow scrambled the electronics?

I have a TPMS tool (yes I'm a tire geek) which allows me to connect with each sensor directly, not through the car's systems. It will instantly tell me the pressure, temperature, serial number, and battery condition of each sensor when I read them. But also this is a $500 tool which most people don't have - but most shops do.

In this case I would return to the Firestone store and ask them to use their tool (assuming they have one) to verify sensor condition. It takes a technician about 5 minutes to do the whole car and they can just do it in the parking lot. I would hope they'd be willing to check that out since the problem started when you brought your car there.

-Bob C.

Originally Posted by BillBoost37

Fixed that up for ya Bob.

You da man. And let me know when you need some wheels balanced.