355 Teves brake system error

Hi everyone , you will have to bear with me a bit on this one as I’m in pretty deep trying to resolve this problem !! So we have a customers car which has intermittently had abs problems which have now become a permanent error , the vehicle is not priming the the pump at key on and the abs light is on , when I put the diagnosis fuse in the error is 2.1 which is for the main solenoid , I have tested the solenoid , it has been ultrasonic cleaned , this didn’t cure the problem , I have done comparative testing with a known good car , resistance check was 4.5 ohms on both vehicles , I have pulsed the valve while recording the amperage , both valves are 2.7 amps in operation , in desperation I have swapped out the whole brake unit including the ECU and the pump and accumulator assembly but still cannot revive the system ! I have had the breakout box on the system and run through the wiring , GND is good on terminal 1 , +12v is present at key on at terminal 2 , my first main error is terminal 3 is not being energised so the main relay is not switching on , as I understand it terminal 3 is energised from the main relay by an output from the ECU terminal 8 which is also not energising , I can only simulate this error on the known vehicle by un plugging the main solenoid creating an open circuit , I can’t fault the wiring unless I’m missing something ! It would really help to be able to understand the operating logic of the system as it may help working out a start point for diagnosis !! I have bridged terminal 8 to terminal 2 , this brings the system to life with the pump cutting in and out when the brake pedal is pumped so I’m pretty confident the problem is not related to the pressure sensor . If anyone has any ideas they would be gratefully received!!

 

Many thanks for the wiring diagram , much clearer than the original ferrari one i am currently using !! I currently have the wire to pin 18 isolated from the 35 pin plug and have the solenoid connected via the breakout box and i am using a chassis ground , so i have completely eliminated the vehicle harness. The error is still present . I feel like there is something else in the system that is creating this fault but not obviously linked ? I have read on another chat that a fault relating to the starter solenoid had created a random ABS fault but looking at your diagram this is not likely on a euro spec vehicle altough this is a fairly odd spec car being a motronic 2.7 spider with extended resonator tubes on the inlet which i have only seen on this car ! I will try and find out its original market destination .

 

It is a UK supplied car

 

Thank you again for your reply , the 12v supply at pin 2 is present at key on and also engine running , we have swapped out all three relays and the diode , I can try bridging out the relay out tomorrow when I’m back in work but as you have eluded to this probably won’t change the fault . We swapped the ECU from another known good vehicle and at first key on the 2.1 error was present . The WSM says the vehicle needs driving to clear the fault memory but as the pump isn’t priming unless I bridge pins 2 and 8 this isn’t really possible , I could put this ECU on another car to clear down but the one we tried has been returned to the client and I currently don’t have another Teves 355 available for testing . We may have to ask nicely and borrow the vehicle for some comparative testing
I will definitely take you up on your offer on wiring diagrams , I do have a fair few already , I’ll check what I have and can list out for anyone who needs them .

 

I have removed the valve and it has been ultrasonically cleaned while being pulsed, the resistance is 4.5 ohms at the 35 way plug on the ECU , i am measuring this via a break out box , i have also tried removing the wire from the 35 way plug and completely bypassing the loom straight to the valve , i have also swapped out the complete brake ABS unit with another car and the fault is still present , i have cleaned all the terminals so am at a bit of a loss as where to go next , I think i may try scoping the solenoid on this and a known good vehicle to see if there is any think strange happening at key on !!

 

I did swap the entire unit including the fluid reservoir so level switches have been eliminated , my plan is to scope the sensors and solenoids as I key on and try and find what is different between this vehicle and a known good vehicle , I will be interesting to see what the ECU actually puts out as a test signal to each component, then hopefully I can figure out on a known good vehicle where the difference lies !

 

So after a bit of a curve ball at the start I have got to the bottom of this ! I have hooked up the scope to see what signals are coming out of the ECU and have found that the it is not generating the test check signal to the main solenoid , fortunately we had another teves 355 in today and I jumped on it to get some reference measurements, on the known good car the ECU generates a 12v duty cycle which is continuous all the time and not just a key on test which makes sense for the safe function of the system , scope is definitely the best way to check as a multi meter will only show about 0.2v , I have attached a photo of the graph from the pic scope , we were curved balled on this problem as we had swapped out the ECU from another vehicle and it didn’t cure the problem although that particular car has had random ABS problems so we may of just been unlucky at the time of test !! Our next problem is where to source/ repair this ECU as they are no longer avaliable and eurospares want nearly £4000 for a second hand one !! If anyone has any company’s they have had a good experience with ECU repairs I would be grateful for your recommendations. Thank you for all the input from everyone, it’s been really helpful Image Unavailable, Please Login

 

I think we may of struck gold and found a NOS ECU located in Germany for €2000 , we have ordered it , will update when it arrives , really appreciate all your help . Will save all this info for future reference

 

Hi guys , sorry for the long overdue update !! As I have now had two teves 355’s with intermittent frustrating faults I thought I would update you with my findings . On the original car the replacement ECU did cure the problem but we had a further intermittent fault prior to returning to the client , the vehicle would intermittently not prime up and using the fuse in the diagnosis holder did not bring up any flash codes , after some comparative testing I found that the large green pressure sensor was not supplying an earth to allow the pump to build pressure. The slight curve ball I have discovered is that according to the workshop manual when there are no faults with the system the fault memory is deleted when the vehicle is driven over 40kph , this is not always the case so you can be left looking for a previous fault that is no longer present!! This leads me into the second car that I have had an intermittent fault with , this vehicle would also flash previous codes even though they were absent , I proved this by disconnecting one of the wheel speed sensors and then reconnecting it , the fault did not clear from the ECU after a drive cycle ! This car was driving fine with the pump priming but occasionally flashing the ABS light , after much frustration I managed to trace the fault again to the large green pressure sensor but with different symptoms . There is a check circuit from pin 9 to pin 10 which runs through the level sensors in the master cylinder reservoir and also passes through the pressure sensor , it is a12v lin circuit which actually runs at about 7v when everything is connected and working correctly , the pressure sensor would occasionally go to ground internally which then brings the warning light on , there is no flash codes for this so no error is recorded! This pressure sensor is not available from Ferrari but I did manage to cross reference it with a Porsche and managed to order it on an exchange basis from the main dealer , they are not cheap !! So if you have any weird intermittent faults have a good look at this sensor !!!!