Technical Fiat can't read ECU codes.

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Technical Fiat can't read ECU codes.

TedR

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Hi - I have an airbag warning light on my old Fiat Brava 1.6 (W) and my car cannot pass the MOT.

My local Fiat dealer can't get their system to communicate with the ECU (they don't know if the car is too old) to check/clear the fault codes.

Does anyone have any suggestions for who might be able to help or other things they could try?

Thanks

Ted
 
Welcome to the forum TedR.

A Fiat Main dealer should have no problems whatsoever using the Examiner diagnostic machine. I had an independent garage use a Snapon branded reader on mine before.

I use Multiecu scan as it happens I just read my ABS unit this morning.

Here is their webpage.
http://www.multiecuscan.net/SupportedVehiclesList.aspx

I use a iDiagnostics branded USB KKL cable and 16pin to 3pin convertor like this.



I have found with my Teve's ABS unit in my car does not store codes so the ABS warning light must be on when you read the ECU to get a result. Are you near Manchester? I might be able to use my reader on it.

Hi - I have an airbag warning light on my old Fiat Brava 1.6 (W) and my car cannot pass the MOT.

My local Fiat dealer can't get their system to communicate with the ECU (they don't know if the car is too old) to check/clear the fault codes.

Does anyone have any suggestions for who might be able to help or other things they could try?

Thanks

Ted
 
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Hi Adrian - thanks for reply and offer. Unfortunately I am down in London area. I did take it to the main Fiat dealer in North London, so I probably need to find in detail what they tried to do. But can I just ask a couple of stupid questions?

1. There are separate engine ECU/ABS/Airbag units and several connectors in various places. To access/clear the airbag fault is that only done through the airbag unit or does it involve speaking to the main ECU unit?
2. Do you think if they can't connect it's more likely to be just a simple dodgy wiring connection somewhere or it more likely they have the wrong connection/communication settings?

Thanks for any advice

Ted
 
The three ECU's Airbag, ABS and engine management are all separate to each other. Though the airbag wiring is designed in such a way that the Airbag error light will come on if the fuse is simply taken out.

The airbag ECU connector is under the centre console as shown in this picture of a Fiat Coupe the end will be covered by a cap/protector;
P1020692.jpg

Recently another member could not connect to the Airbag ECU because the wiring harness pins had corroded from coolant dripping out of the heater matrix onto the ECU. He had to replace the ECU.

If you have a passenger airbag they have a sensor in the passenger seat to detect a person. If that sensor is broken it can trigger the warning light.

I could not find a diagram showing the location of the ABS and ECU diagnostic connectors so I labelled them in this pic;
bay.jpg

If your local fiat plugged the reader into the correct port and it didn't connect it might be corroded pins.
 
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Hi Adrian - thanks for the photos. I guess the first thing I should do is look for any corrosion in the wires to the airbag ECU. Then I might try and buy a code reader. I'm hopeful that the reason the light is on will be the wiring under the seat - I did move something that had got slightly entangled under the passenger seat the day before the problem arose.

Ted
 
Hi Ted,
Almost certainly you have disturbed a connection under the seat. This could be the seat switch, but is more likely to be a seatbelt pretensioner connection (or side airbag if your car has them). The seat switch just shows open or closed and the ECU can't tell if it wrong as it has no other way of telling that the seat is occupied. You could try plugging the seat belt in to rule it out. The airbag and pretensioner actuators (squibs) have a nominal resistance and the airbag ECU checks this resistance is within limits. even a bad connection, not even a complete open circuit, or a short circuit will give an error light. Often just pulling the plug apart and back together will cure the problem. A little contact cleaner (or WD40 at a pinch. Yes, I know it's not ideal but it works) on the connector pins can help. Just a tiny amount, don't spray it everywere.
My wife has done this to two of my cars by shoving her case of CDs under the seat
rolleyes.gif


Robert.
 
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Hi Robert - thanks for tip - have you ever managed to get this to reset the light though - I was under the impression that the fault gets stored in the memory even if it disappears?

Ted
 
Hi Robert - thanks for tip - have you ever managed to get this to reset the light though - I was under the impression that the fault gets stored in the memory even if it disappears?

Ted

Hi Ted,
On my 2001 Marea repairing the connection cleared the fault light on the next start-up, but the fault code stayed stored in the ECU until reset. My car had the later 16 pin OBD connector. So I can't be sure about your slightly earlier system. Does no harm to try though. Disconnect the battery and wait 10 minuites before working on any part of the airbag system. It can cause serious injury of it goes off at the wrong time. Disconnecting the battery may also help with resetting the warning light. Do not use a test lamp or buzzer for fault finding either they can supply enough current to set off a squib. Use a digital multimeter if you have to do more than look.

HTH,
Robert
 
Hi Adrian if you are still there. So thanks to your suggestion I've purchased the 3pin to OBD cable and the blue OBD to USB cable and downloaded Multiecuscan.

Before I try it all I just have some slight queries about the various ground connections in these cables and to the battery.

In my 3pin/OBD cable, both the 3-pin signal ground (middle pin) and the black croc clip are connected to pin 5 in the OBD connector. Pin 4 is not connected.

In my blue OBD/USB unit (which is advertised as for VW/Audi but users report using it for Fiat) pin 5 is not connected but the circuit board is instead connected to pin 4.

Presumably I need to modify this slightly - perhaps by joining pins 4 and 5 together in the blue OBD unit. How do you have the signal and chassis earth connections made in your cable - I notice that you don't seem to connect the black croc clip in the photo.

Thanks for any advice

Ted



How

Presumably I should solder
 
Presumably I need to modify this slightly - perhaps by joining pins 4 and 5 together in the blue OBD unit. How do you have the signal and chassis earth connections made in your cable - I notice that you don't seem to connect the black croc clip in the photo.

Thanks for any advice
Ted

Hi Ted,
I know this was addressed to Adrian, I hope you don't mind me jumping in. Pin 4 is Chassis ground and 5 is signal ground. You are correct in your deduction that you need to connect them together. You will also have to connect the 12V battery supply to pin 16 of the OBD interface.

Robert.
 
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Hi Ted,
I know this was addressed to Adrian, I hope you don't mind me jumping in. Pin 4 is Chassis ground and 5 is signal ground. You are correct in your deduction that you need to connect them together. You will also have to connect the 12V battery supply to pin 16 of the OBD interface.

Robert.

Hi Robert - thanks for the reply - this is what I thought. The only thing I don't really still understand on doing a bit more online research is that some people seem to get these VW/Audi OBD cables to work without mentioning any modifications, whereas some can only get them to work with modifications.

Ted

Ted
 
@TedR i accidentally bought a VW group vagcom USB cable, i modified it by joining the pins 4&5 together, with my 3pin adapter, it works fine now.
all my info came from here, 5 minutes with a multimeter and soldering iron.

Hi - yes this is basically what I did and then I had no problem connecting first time and clearing the problem (as suspected it was intermittent glitch in wires under passenger seat). Thanks to everyone for their help.

I don't know why the Fiat dealer claimed to have problem - the 3pin connector in the car looked suspiciously like it had never been connected before since it was still embedded inside protective foam when I got to it. They did appear to have removed the side of the centre console though since they'd removed the trim pins.

Ted
 
Great post! Very informative. I have had an airbag warning error for a week or two and have been trying to clear it using an ELM Bluetooth interface with a 3 pin adapter. Works fine on the engine management but seems the airbag ECU does not support it (from multiscan website). Also, didn't realise there was a separate connector for the airbag but found it when I saw this post. Have ordered a VAG cable (one with the switches, instead of getting all the adapter leads as it is a bit cheaper....probably not the best solution...but oh well...) so will hopefully be able to find the error soon. Once again, thanks for the post.
 
varesecrazy Thanks! :D

Will do that when I get them (probably only end of Feb). It is the normal 3 pin adapter which is the same for the engine management, located to the side of the center console as shown in the 4th post of this thread by Adrian Bravo. (y)

Will give let you know if I come right.
 
Great post! Very informative. I have had an airbag warning error for a week or two and have been trying to clear it using an ELM Bluetooth interface with a 3 pin adapter. Works fine on the engine management but seems the airbag ECU does not support it (from multiscan website). Also, didn't realise there was a separate connector for the airbag but found it when I saw this post. Have ordered a VAG cable (one with the switches, instead of getting all the adapter leads as it is a bit cheaper....probably not the best solution...but oh well...) so will hopefully be able to find the error soon. Once again, thanks for the post.

Hi,
The ELM 327 interface is "smart" and decodes the data on bus into numbers / text. This means it only works with standarised protocols, regardless of the software used. The VAG-COM interface is "dumb" and just changes the the voltage levels to suit the computer. This menas the software can work with non-standard protocols like the early airbag system. The VAG-COM does not support CAN so is of limited use on newer vehicles.

Robert G8RPI.
 
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