Toyota Corolla cleaning electrical contacts


#21

I made a file (sort of)using a copper wire with slanted notches cut on it. Copper being soft, it gets blunt quickly, but it seems to be somewhat helpful. Can’t really see inside the female connectors to say for sure if it was helpful. When I tested continuity, it showed continuity. So, I guess it was helpful.

I have to rule out whether the issue is a connection issue between the srs module and the wiring harness. If that is not the case, I am going to send the module for repair or reset. I hope that should fix it, else I need someone to tell me how to remove the bulb for the srs light from the dash :slight_smile:


#22

One of two things, in my opinion

1 . . . the srs module is functional, but the code(s) need to be cleared for the light to turn off and remain off

2 . . . the srs module is essentially dead because it was underwater, and no amount of cleaning will revive it

Do you even have a scanner capable of reading and clearing Toyota srs code(s) . . . ?


#23

Could you reassemble the system and see if the car’s computer now communicates with the module? It is possible that you still have a fault elsewhere, in the seatbelt linked sensors or in the sensors in the front bumper area.


#24

The pressure sensor on the passenger seat seems faulty. The occupancy light stays off even when someone sits in the passenger seat. Could that trigger the srs light?

Is it safe to unplug the seat pressure sensor to see if that turns off the light or will ot trigger the air bags?

There are 3 connectors under the seat. Any idea which one to unplug (in case it is ok to remove it)?


#25

You really need to find a wiring diagram for the SRS system. I found reference to one on the AutoZone website through Google, but the diagram itself did not download.

As far as I know, which is about nothing at all, you can unplug that cable under the seat. I have unplugged all the cables under my car seat to remove it, no problem. The key was off, of course.


#26

How do I delete this post?

Sorry , my bad, thanks NYBo for catching it.


#27

The discussion is about the airbags in the car.


#28

The SRS light is sometimes tripped by debris in the buckle. The belt doesn’t make enough contact with the clasp to register as seated. Disassemble the buckle and see if there is debris in there. I had a similar situation on my Accord.


#29

I will check the seat belts to rule out problems with it. I suppose I can do continuity checking for this?

What I would like to know is if the srs light can turn off on it’s own once the problem is fixed or does it needs to be reset.


#30

The srs module performs tests every time you turn on the ignition

If all is well, the light will then turn off

If all is not well, the light will stay on

If the module is dead, or there is some wiring problem to the module, such as frayed wiring, blown fuses, etc., the light will stay on

Don’t take this the wrong way, but I suspect your module is bad, because it sounds like it was essentially underwater


#31

The wiring for the seatbelt and passenger sensors is under the seat, lower in the car than the module, so it could easily have been soaked. Cheap to check it out, too.


#32

I too realize that the module could be faulty. But, I have to first rule out the possibility that the wiring could also be at fault.

I contacted one of places that repair srs modules. According to them, modules that have water damage cannot be repaired. My option is to get a new module and do fresh programming. They said, the srs light could also be due to problems with the seat belt buckle and weight sensors on the seat.

First I am trying to see if the seat belt buckle is faulty. I see no sign of corrosion on it. When I disassembled it, I was intrigued at the presence of a neodymium magnet in it. When the seat belt is latched on, it pushes the magnet over a tiny circuit board. Two wires run from this board to under the seat. I measured around 775 ohms across the wires in the unlatched position and around 771 ohms in the latched position. The resistance changes very slowly. Never thought that the seat belt circuit works using magneto resistance.

Anyone worked with something like this?
What is the expected resistance across the wires coming from the seat belt buckle (in latched and unlatched position)?


#33

Try this . . .

Connect a scanner or code reader that is capable of communicating with the srs module


#34

I connected a wire between the Tc-cg terminals and read two codes - 32 and 31.
Previously when I took the car to the dealer, they were unable to communicate with the srs module to even get a code reading. I cleaned the wiring harness and the male connectors of the module.
Is is possible that the srs module is working fine, since I am able to communicate with it now?

My understanding is that code 32 is related to the occupancy sensor and 31 is more of a general code. I read somewhere that if code 31 shows up with other codes, I need to fix the other code first. Is that right?

I noticed that the resistance across the seat belt latch on the passenger side doesn’t change when the latch is on or off (showed around 790 ohms when I measured yesterday). Does any one have a resistance reading for the passenger side seat belt latch on a similar year Corolla? Couldn’t find those numbers anywhere on the Internet.

Any suggestions on how to fix the code 32?
Thanks


#35

I removed all connectors under the passenger seat and I didn’t find any sign of corrosion or water damage (except for the rust on the metal under the seat).

There are only 2 suspects related to the passenger seat - a black module where the weight sensors are connected and the weight sensor mesh.
This black module is on the underside of the passenger seat towards the front with two multi-pin connectors. One connects to the 4 weight sensors on the 4 corners of the seat and the other is an output going to the srs module. I don’t see absolutely any sign of corrosion of sign of water entry in this.

The next suspect is the weight sensing mat, which is sandwiched between the seat foam. I don’t want to mess with it if I don’t have to. But, I would like to test it to see if it is working.

Suggestions?


#36

To see if the sensor is working check the resistance of the sensor while the seat is empty and then while sitting in it. There should be a significant change in resistance.

The other seat sensors you measured don’t seem to be working correctly. I don’t know what the resistance readings should be but you should see a fairly significant difference between the two readings.


#37

I think you’re talking about the seat belt sensors where the resistance seemed to change very little. I would think it would change a whole lot, maybe even from an open circuit with no belt to a circuit with some resistance when the belt is buckled, but the current to that switch might only run when the weight sensor is triggered with a passenger.

Is the seat belt warning light on? Is the car chiming or beeping?


#38

When someone sits on the passenger seat, at first the light showing that there is a passenger in the seat turns on and then off. The seat belt sign stays off all the time.

All this time, I didn’t think the Occupant detection module under the passenger side could be bad because the terminals looked so clean. Running out of ideas, I decided to open it up, knowing very well that if I mess up I might have to shell out about $250 for a new module. Upon opening it, I think I found one of the problems related to the srs light being on (there could be more). There was heavy corrosion on the circuit board even though the male connectors were sparkling clean. I am going to see if I can find one from a junkyard. I am thinking that I might have take it somewhere and re-calibrate it too.

For all Corolla owners, here is a warning. Apparently, this occupancy detection system is extremely prone to moisture damage and unfortunately it sits low, closer to the floor. There is some kind of rubberized coating on the circuit board (which I haven’t seen in the ECU or SRS modules that I have opened up so far), which means that Toyota knows very well that this module will have moisture entering it. But that coating is not good enough to provide moisture damage protection. Most washing machine circuit boards are embedded in some kind of hardened resin to protect them from moisture entering them (at least the ones that I have seen). Compared to that Toyota is doing an extremely poor job at protecting this circuit board.

Next time, I am putting a bead of silicone along all possible entry points for moisture or at least putting a plastic bag and taping it up.

About the seat belt latch, I did not measure any difference in resistance when the latch was on or off, making me think that it could be faulty. However, I could just be assuming that it is faulty. The last thing that I want to do is to throw parts at the problem, hoping that something will fix it.

So far, my conclusion is that the occupancy detection module is definitely faulty and the passenger seat belt latch might be faulty. I am still not sure about the seat belt latch. There is no sign of damage or corrosion even on the circuit board. Could it be that the seat belt sign is not coming on because this module under the seat is bad? or is that an entirely different system? I will try to replace those and see what happens. At least the srs module is communicating to give me an error code (previously, the srs readers weren’t able to communicate with it).


#39

There are six pins for this connector (coming from the weight sensor). I am still looking for a wiring diagram, to know which pins to measure across.


#40

bending and misalligning the male/female connectors is a costly problem that I have long avoided by applying a lubricant like this

to the male contacts then connecting the male and female and repeatedly pressing the connection fully together then repeatedly pulling the connection out about halfway ten back to fully inserted. In a few strokes corrosion is cut through at the contact areas and future corrosion is prevented.