Passenger weight sensor question

[BigTasty]

SRS code showing it’s bad but I saw a TSB that says there’s a whole harness assembly replacement etc but I also saw that you can just buy the sensor itself

Which route can I take?

[VStar650CL]

Is this on your '10 FX, or something else? What code?

[BigTasty]

My fault it’s the ‘13 jx35

No codes but the srs light is on

I referred to this tsb

https://static.nhtsa.gov/odi/tsbs/2017/ ... 8-9999.pdf

[VStar650CL]

Is the light solid or flashing? If it's flashing, you need to reset the Bag Brain. There's a bulletin for that:
https://static.nhtsa.gov/odi/tsbs/2018/ ... 6-9999.pdf

If it's solid and there are no codes in the Brain, then something is very wrong.

[VStar650CL]

PS - Are we talking about the red SRS icon in the cluster, or the yellow passenger bag indicator (PABI)? If it's the PABI then the first thing to try is a Zero Point Reset, but I don't know of a way to do that without an SRS-capable scanner.

If you want to post or PM me your VIN, I can run it through ASIST and see what prior work was done. There were two OCS recalls on the JX, and those would still be free if they were never performed.

[BigTasty]

That’s what it’s doing the red light is blinking

I’ll try the procedure you posted

I diss try the zero point reset but I guess since it’s in that service mode it won’t allow it

This is the only code I could see from the srs system was an old stored B1022

[VStar650CL]

I'm pretty sure flashing on your ride can only mean diag mode, the lamp would be on solid if it was lit because of a code. Use the stopwatch app on your phone or a watch with a sweep second hand when doing the on-off stuff, the Bag Brains are very fussy about the timing. I'm good at it, but even I need to do it four and five times on occasion before it works.

[BigTasty]

Tried the procedure like 10 times and the light is still blinking

I used my apple stop watch

On 7aecs
Off 3 seconds

3 times

Still blinking

[BigTasty]

I wonder if I am doing something wrong

[VStar650CL]

Sometimes doing a "hard battery reset" and then doing the reset procedure helps. We did run into one Brain which we couldn't reset no matter what we did, evidently it was corrupted internally.

[BigTasty]

Sometimes doing a "hard battery reset" and then doing the reset procedure helps. We did run into one Brain which we couldn't reset no matter what we did, evidently it was corrupted internally.

10-4
I tried reseting it agian, and nothing. So I guess its time to replace the module?

Which part would it be? the diag module? 988203JA0A?

[VStar650CL]

That looks like the right part, yah. There are supersessions on the number. Nissan usually calls the Bag Brain a "Center Sensor" for whatever Japlish reason.
https://www.infinitipartsdeal.com/parts ... 3jh9a.html

[BigTasty]

I sent the module in for repair and they got it fixed so it’s back on its way I’ll post when installed and if it fixes the issue

[BigTasty]

I just got the module back and installed it, cleared any codes present and the air bag light still flashes and I can not reset the zero point. I didn't try the reset feature yet with the on/off 7 seconds thing.

Possible that I need to inspect the wiriing from the occupant sensor to the module? or the actual sensor may be faulty?

[VStar650CL]

Sounds like they didn't actually repair anything. The Bag Brain only has ignition power (no battery) and the only thing I'm aware of which can make the icon flash is diag mode. You can check the OCS just by putting weight on the passenger seat and watching the yellow PABI indicator. It should go out at about 60~80 pounds, if it does then there's nothing wrong with the OCS.

[BigTasty]

ah dang, I'll check the light when I get back. I was hoping to not have to buy a new brain

Thanks for the help.

[BigTasty]

sat my big butt in the seat and the light did not go off. So maybe the sensor is bad or the wiring?

[VStar650CL]

Or maybe the Bag Brain isn't communicating. I'll have to look up the diagram tomorrow, in some systems the Brain drives the PABI and in others the OCS drives it. I'll post back.

[VStar650CL]

Okay, it's the Brain which drives the PABI on your JX. However, it looks like the lamp is set up a little different from other N/I products. Is the flash rate 1Hz (1/2 sec on, 1/2 sec off)? That's different from diag mode, which is 2 sec by 2 sec. If it's 1Hz with no codes present, it's telling you it lost the zero point for the passenger seat strain gauges. You need to perform a ZPR (Zero Point Reset) on it. I'm not sure if that means a dealer visit. You definitely need a capable scanner to perform it, but NDS-III or some other common app may be able to do it.

[BigTasty]

I finally had time to get the wiring diagram to see how it looked. I am going to test the circuits from the two weight sensors to the occupant module under the seat, and then I'll test the circuits from the occupant module to the brain box. I'll check the fuse powering the OCC module first. but here is the diagram.

I am wondering if the module is bad under the seat. I guess if the circuits all test good, that may be the issue.

[VStar650CL]

The OCS strain gauges just need to be moving when you apply weight. They usually read something like 1.5~3V with no load, but there's no fixed value. That's what ZPR is for, to give the OCS Controller a baseline reading with the seat unloaded. If you find either sensor flatlined at 0V or 5V, or there's no movement with load, that will be your culprit. I'll be surprised if there's an issue, though. The OCS's are pretty good at recognizing faulty sensors and there's almost always a code for a failed one. Sometimes it's a generic "abnormal voltage" code like B0A00, but there's almost always something.

[BigTasty]

Tested the sensors and I’m getting reference voltage and 1.9 when plugged in

Im kinda at a loss now lol

[VStar650CL]

The 1.9 is pretty normal, but do both signals move when you apply weight to the seat? That's the key to whether the load cell is good or not. If the voltage doesn't move, the sensor is shot.

[BigTasty]

just to make sure I checked the volatge to the OCS unit undert the seat and the wiring going to the SRS brain, and that's all good.

So I am wondering if the module under the seat is the issue?

[BigTasty]

The 1.9 is pretty normal, but do both signals move when you apply weight to the seat? That's the key to whether the load cell is good or not. If the voltage doesn't move, the sensor is shot.

I will double check, but I do not think the voltage moved when I touched the sensors by hand.

[VStar650CL]

It's not a matter of touch. They're load cells, the voltage moves when there's a load. I have a 10" cinderblock under my bench that I use for a faux 4-year-old, but you can also just have somebody sit in the seat.

[BigTasty]

It's not a matter of touch. They're load cells, the voltage moves when there's a load. I have a 10" cinderblock under my bench that I use for a faux 4-year-old, but you can also just have somebody sit in the seat.

I did some more testing. FL sensor is 1.25v with out weight then goes to 1.5v with weight. the FR goes from 1.25v without weight to .9v with weight. So they are sensing movement. not sure if in spec or not. I also replaced the SRS Seat Sensor Mat Occupant Module OEM For 2013 Infiniti JX35 988563JR0A and that didn't fix anything either.

What do you think? I am starting to think that the company that fixed my SRS main module didn't repair anything.

[VStar650CL]

I hate to agree, but that's what it sounds like. Nissan doesn't publish a spec for voltage movement of the sensors, but usually when they die it's because the internal resistor which flexes under load either shorts or (more often) goes open circuit. Then you don't get any movement at all, they just flatline at 0V or 5V. So it sounds like yours are good.

[BigTasty]

I hate to agree, but that's what it sounds like. Nissan doesn't publish a spec for voltage movement of the sensors, but usually when they die it's because the internal resistor which flexes under load either shorts or (more often) goes open circuit. Then you don't get any movement at all, they just flatline at 0V or 5V. So it sounds like yours are good.

Yep...that's what it sounds like...would you happen to know if I can swap a used srs main module with a use good unit? Or does it have to been a virgin unit?

I can always get the eeprom wiped on a used one if need be.

[VStar650CL]

A good used one is fine as long as it comes from the same MY. Don't rely on the part number label, Nissan uses the same Bag Brains in multiple applications with the only difference being firmware.