348 ABS question

Planning to send my ABS electronic unit to BBA for rebuild. Can the car be driven without the electronic unit? I have no ABS currently so that is not a concern. Thanks, John.

 

Thank you No Doubt. I suspected as much but want to insure no damage to any related systems. John.

 

Fatbillybob, http://www.bba-reman.com/ rebuilds the ABS electronic units as well as Ferrari ECU’s. I have never used their services but have heard good results from others. I have had the ABS dash light on for a couple of years now(No ABS function). I have checked every electronic connection and cleaned with Stabilant. Bled the complete system twice. Ran the codes. My error message indicated a “Faulty Right Front Return Valve”. I have been told the bulk of these error messages are attributed to defective ABS units. Valve failures are supposedly rare. I don’t know from my limited experience if this is accurate or not. I have not checked the solenoid valves for function. Appears I need a “Special” Ferrari tool to activate each valve function per the workshop manual. Any advice or experience you have would be appreciated.

 

Thanks No Doubt. My understanding of the system is the valves are a part of the Master Cylinder unit. I don’t know if they are removable components. The rudimentary understanding I have is there are 3 valves, right front, left front and rear. From my research Ferrari tests the valve function with a Break-out Box(correct term?). They isolate the valve function to wheel. Activate valve function closed and open, brakes grip or not with pedal pressure.
I have been contemplating “jumping” the connections to activate the valve functions but fear screwing the problem up more. Inexperience can do that!
I purchased a used 348/ 355 complete pedal box assembly cheap. Looks like a royal pain to change but may be an alternative to changing the ABS electronic unit based on your input.
I do have a question. I understand your statement regarding backup ABS computer function but if the unit malfunctions and incorrectly "reads" a faulty valve, will the 2nd computer function correct the error?
As always, thanks for the help. John

 

Thank you Noah. Reviewing the drawings No Doubt posted I believe the valve assembly is "A" in the middle document. This appears to be a removable assembly. Attached to the brake cylinder unit. I have a complete pedal assembly in my basement. Perhaps disassemble that unit, switch the valve assemblies and see if the problem is resolved. Shame, I just flushed and bled the whole system. As you observed, my ABS light is on resulting in no ABS function but full standard brake function. Red light is not on. I assume the assemblies are sealed via “O” rings. Standard “O” ring material sufficient or does brake fluid require another base material? Question may be premature, seal method will become apparent when disassembled. Regards, John.

 

Thanks all. It has been a couple of years driving around with the light on and the luggage liner in my basement because I was going to fix the problem! If I recall correctly it is the #25 fault code. Reread my workshop manual last night. Appears the unit will not read any further codes when it detects a valve fault until that specific fault is corrected. If my understanding is correct this indicates the possibility of other fault codes not shown. May try the valve function test procedure this weekend. The manual gives a schematic showing pin number and function at the connector. The test procedure details jumping 2 pins with a 10 amp fused line. The next step indicated is to jump 2 pins as listed to test each valve function. Key in the “Marcia” position. Brake pedal pressed. Tested wheel should either be free or braked depending on ABS valve tested. I was curious if the valve function could be tested at the connector to the solenoid valves themselves? This appears to be a 6 pin connector. There are 6 valve functions(3 sets of 2, return and feed). If the solenoid valves are grounded to the brake assembly body, power each pin with 12 volts to activate the valve? This appears simple but my concern is damaging the solenoid valves by extended power cycles. They are designed to power up and down 15x a second. I will be power them up for several seconds to test. Or I could be completely off base. Wouldn’t be the 1st time! Thanks, John.

 

ABS Update. Picked up supplies at Radio Shack to fabricate fused jumpers to test ABS valve function. Bought 3 Buss type inline fuse holders, Buss 10 amp fuses and alligator clamps used to test micro circuit boards. The clamp ends are only about 2mm wide x 0.5mm thick rough estimates. They easily fit in the ABS ECU blade connectors without distorting the receptacle. Micro Clips #270-373. Taped the main body of the alligator clamp to prevent any shorts.

Using the Ferrari workshop manual procedure, I disconnected the 35-pin connector from the ABS electronic control unit. The manual shows a “special” tool, a 35-pin breakout box to test function. I bridged the specified pins directly at the connector with my fused jumpers.

Initial test is the main ABS valve function. Connected Pin #2 and #8. These are constant, they power up the valve feed pins #3 and #20. Then connected #3 and #18. Press brake, turn key to the “Marcia” position. Brake should kick back and stiffen according to the manual. Subtle kick back and marginally stiffer feel. Repeated because the specified reactions were subtler than I expected. Manual was emphatic that the key should never be on for more than 30 seconds during any of the tests to prevent overheating. Main valve system appears to function fine.

Even though my code(#25) indicates a faulty right front return valve I performed all 6 valve tests. Right front return, right front delivery, left front return, left front delivery, rear return and rear delivery. I will only detail my test of right front return; the other tests are detailed in the manual.

As stated above, #2 and #8 are always bridged for all the tests. To test right front return I also connected #3 And #34 In addition #20 And #15. I precut boards to prop the brake pedal pressed to check wheel function when I got out of the car. Easier to test with 2 people, no brake prop needed with an assistant. Checked to insure the wheel was locked with the brake prop in place prior to test. Test procedure: Turn key to Marcia position, press/ prop brake. Right front wheel should now be locked. Turn key off, wheel should be free(rotate with brake pedal pressed). All my valve tests indicate no valve fault. All front and rear tested as they should.

Reviewing the wiring diagram the circuits appear to pass through the “Diodes Container” and 2 Relays(System Release Relay and Electronic Unit Relay). Could the problem be a faulty relay? Diodes Container?

Since the tests were performed through the main connector I would have to assume the wiring is not the problem.

This leaves only 3 areas with possible failure. Electronic control unit. Relay failure. Diodes failure. Any and all opinions appreciated.

 

No Doubt, thank you. I checked the Ricambi website for parts. They have the Diode Container for around $50. The other 2 relays are not listed. I will try to source those at an automotive supply shop. If I recall correctly 1 is Siemens and the other ATE labeled. Your offer to test with your spare ABS electronic control unit is most appreciated! I would ask why you have a spare if I didn’t have a spare complete pedal box assembly, 348 shift assembly with cables etc etc in my basement! I tend to, ahem, collect parts as I see them. Thank you again for the help.

 

Hello All, Status Report.
Over the weekend I installed all the relays. Drove the Ferrari for the 1st time this season Sunday to see if all my testing, cleaning etc had resolved the problem. No. ABS light still on. If I recall correctly the ABS electronic unit will reset to a no fault condition if the problem is repaired and you exceed 40kph.
Pulled all the relays and tested function. Test procedure as follows:
After studying the wiring diagram I used pin 85 negative and pin 86 positive. Some of the relays are diode type; correct polarity is critical I was told.
Using my 10 amp fused jumpers from my valve test I tapped 12 volt power from my wife’s Lexus battery. The jumpers were convenient. The micro alligator clamps attached to the relay pins easily and securely.

131939 Pump Relay ATE. Diode type, normally open. Distinct click when 12 volts applied. Continuity across pin 30 and pin 87. Appears OK.

131938 ECU Relay Siemens. Non-Diode type, normally open. 5 pin relay. Distinct click when 12 volts applied. Continuity across pin 30 and 87a when off. Continuity across pin 30 and pin 87. Appears OK.

131940 System Release Relay Hella. Diode type, normally closed. Distinct click when 12 volts applied. Continuity when off(closed). No continuity when on(open). Appears OK.

131785 Diode Box Italamec. I am not sure I tested function correctly. Using what I assume is the diode test function on my multi-meter. With the test function on the meter reads 1.499 volts. My understanding is the voltage should drop when read through the diode. Pin 87a to pin 87c reading 0.476 volts. Pin 87b to pin 30 reading 0.522 volts. Appears OK if I tested correctly.

To Recap:
Pulled and cleaned all connections with Stabilant.
Bled system twice.
Tested all ABS valve functions.
ABS valve function test confirmed wiring shouldn’t be a potential fault cause.
Tested all relay functions.

Unless I have missed something, or 1 or more of my tests are flawed, it appears the Electronic control Unit is at fault.
As always, opinions and advice welcome. Thank you for all the help thus far. John