Hi all, I have a 1991 348. I just noticed that the brake warning light, item 13 in the instrument cluster does not illuminate and extinguish on initial start up of car. ABS light comes on and extinguishes as it should. All other instrument lights work as they should. I have checked the bulb, its ok, checked fuse in passenger footwell, #10, checks good. Has anyone had this problem? Would like to know how this circuit works. Was thinking of removing brake fluid from reservoir and see if it will illuminate as this is a main function of this circuit. Any help appreciated.
I believe on start up, the light is controlled by a test module (marked as "102" in the wiring diagrams). Not sure where it is located. Item 46 in this diagram??? Not sure. https://www.ricambiamerica.com/car-diagrams/ferrari/v6-v8/348-group/348-1989-1992/electrical-boards.html Instead of draining the fluid, it might be easier if you short the pink wire to earth on the connector going to the brake fluid reservoir (pin 2). The light needs an earth/ground. It depends on what tools/equipment you have at hand and whether the plug is easily accessible or not. .
Here are the wiring diagrams showing "102" (earlier 348's) Ferrari 348 ABS Wiring Diagram F348_Fig5_Instruments
If it's like the 355 brake test light circuit, there will be a simple relay inside that test module which is activated by power from the ignition switch (in the start position). The relay puts an earth on the brake warning light. The test module has a pink wire going to it also. If you can find the test module (probably in the passenger footwell), earth the pink wire to see if the light comes on. Check the module pins for corrosion and "percuss" the case to see if the light comes on (the relay contacts may be faulty)
Thanks for the quick responses, I'm going to start by shorting the wire at the brake fluid reservoir to ground, pin 2, I figure that is the big connector at the end of the brake fluid reservoir, that should tell me if the lights working. If that gives me the light, I'll look for the relay that controls the switch. Part 46 in the Ricambi Diagram. I'll keep you posted.
Looking at the Ricambi parts list, it looks like USA warning light modules also contain a buzzer for brake warning (and/or seat belts, depending on the year). It might make the module easier to find.
Found the module, under the dash, drivers side, connector looks clean and buzzer works. . Jumped pin 2 at brake master cylinder (pink wire) to ground, no joy. Kind of stuck now. May go back to dashboard light and check that again.
Could it be relay control relay for ABS during cranking marked 182? Shown in the wiring diagram for the ABS system?
Since the light is not working with a direct short to earth on pin 2, there must be a problem with the pink wiring or the instrument binnacle. I'm assuming the ignition was on during your tests? You need power to the light circuit. The light uses power from fuse 6, but that powers a lot of other warning lights and systems, so it's unlikely there is a problem there. The "182" relay is part of the start circuit. Any problem with that circuit will only affect the light during startup. The earth you put on pin 2 proves the problem is there all the time. You may have to check the continuity of the pink wiring. e.g. Can you check the continuity between reservoir pin 2 and instrument panel pin 12 (right hand connector). Pin 12 is a pink wire. If you have continuity, then the problem is inside the binnacle. Wiring? Dirty lamp base? If you don't have continuity, you'll have to find out which section of the pink wiring is faulty. There is a connector named "106" where most of the pink wiring seems to spiced together, but I have no idea where that is. You could check the binnacle wiring and lamp by putting a voltage on binnacle pins 4 (pin) & 12 (green-white). A small 9 volt battery should be sufficient. You could do a resistance check on those pins, but I'm not sure what the resistance of the lamp should be.
Hey Qavion, could I just put a voltmeter across pins 4 and 12 at the right hand instrument connector and look for a momentary voltage when I turn the ignition key to the on position? Don't want to damage a computer or wiring though? As for the pink wire, it has continuity from the brake master cylinder to the pin 12 on right hand connector. Thanks for the help.
Checking voltage wouldn't really do anything other than check that you were getting power from the ignition system to the lamps in the binnacle (you would also have to ground the pink wire at the reservoir to complete the circuit). If the most of the other lights are working, then you already know you have power. Do you have any spare lamps for the annunciators? Do you just have a voltmeter.... no ohms (resistance) on your meter? If you have ohms, check the resistance of a known good lamp, then disconnect the right hand instrument panel connector and check the ohms on pins 4 & 12 (binnacle side). The ohms value should be almost the same. If not, then you have a binnacle wiring problem or lamp holder problem. Look for pushed back pins on the connector & broken wires. If the 348 is like the 355, the warning lamps will be mounted on long, narrow circuit boards. You may have to remove a protective cover to access the circuit board. Look for damaged metal foil strips on the circuit board, especially under the warning lamp. Make sure the foil hasn't worn away. Use isopropyl alcohol or something similar to clean the lamp contact surface (not WD40) When checking resistance, power must be off the car. Sorry if I'm "teaching granny to suck eggs" here
I've run some checks on the instrument lighting binnacle. Ran a continuity check from pin 12 right hand connector to socket that controls brake lamp. Test good, shows values. On ground circuit, ran from pin 4 to other side of socket, tests good. Have swapped bulbs from numerous other warning lights, all test good. Looked for pushed pins in r/h connector, Cleaned, reset connector, wiggled, no change. All lights working as they should except brake test light. Another thing noticed is that ABS warning light on dash lights for only a second or two. Should light for longer period of time. Before brake light failed, the ABS light and brake light would stay lit for 8-10 seconds while pump was building pressure after not being started for a while. . Now I don't get any delay. Starting to think that the problem is elsewhere, ABS control box? Thoughts?
It's not clear to me if you have done a continuity check on the binnacle wiring with the lamp fitted. i.e. pin 4 to pin 12 (binnacle side of right hand connector). I realise this is difficult without removing the binnacle. What are you using to do continuity checks? A digital meter or something more basic? If you're not getting a brake warning light with the reservoir pin shorted to ground (and the ignition on and the instrument panel connected), and you've carried out the continuity you said you did in post #12, then the problem almost has to be in the binnacle. Image Unavailable, Please Login The only other thing I can think of that would stop the lamp operating would be if the wiring on pin 12 to the reservoir and other sensors was shorted to a 12 volt power wire. If you do a continuity (ohms) check between 4 & 12 (binnacle side of connector), and it shows the same ohms as a spare lamp, then we can take the binnacle out of the equation.... and go looking for shorted wiring. It's unlikely, but the test module may be somehow putting out 12 volts instead of an earth (at all times). You could try disconnecting the test module and doing the reservoir test again (pink wire shorted to earth/ignition on). Check the wiring going to the plug on the test module. e.g. the wiring on the back of the plug may be shorting out. Let's get the brake light sorted out before looking at ABS stuff. I can't explain the ABS light delay unless the ABS reservoir is simply holding the pressure between ignition on/off cycles.
Actually, if you do this check and you get zero volts (or close thereto), it would tell you that the pink wiring is somehow shorted to 12 volts. If it's easier, you could could check for 12 volts at the reservoir pink wire (plug disconnected). If there is 12 volts see if that voltage is present with ignition off and on. This would help with faultfinding. Don't worry about blowing up your meter or the car when checking voltages unless it's a voltmeter which has a manual section for voltage range. When checking resistances/continuity, however, you may damage your meter if the circuit has power on it or the meter may give a false reading.
Had binnacle out, pin 12 (R?H connector) to bulb socket, circuit board side, shows coninuity. Pin 4 R/H connector ground to other side of bulb socket, shows continuity. Im using a fluke digital volt meter. set on resistance. (ohms) Master brake cylinder (pink wire) showing 11.65 volts DC with ignition on. Shows zero volts with ignition off.
Interesting. It seems like the pink wiring is shorted to a power wire and the source of the 11.65 volts is related to an ignition powered system. Unless we can break up the pink wiring into pieces, it might prove difficult to track down the problem. I wonder if anyone knows where the dashboard-ABS connector is? Equipment number 106. It may be near the bulkhead (between the cabin and the frunk). Do you still get 11.65 volts with the dashboard plug disconnected? This would eliminate a shorted lamp holder. (EDIT: I think the only power source for the test module is start power (on the white wire), so perhaps we can eliminate a short to power on this) Miroljub, if you're following this thread... Have I overlooked anything obvious?
I just realised the voltmeter is not in parallel with the circuit if you do this. Voltmeters must be in parallel with the circuit or component being tested. The voltmeter is probably just detecting the normal power going to the binnacle. Perhaps you could repeat the test with the binnacle disconnected?
My comments: The ABS light will stay on for longer only when the fluid pressure has gone down and while the ABS pump is running (you can hear it humming) to bring the pressure up. The pressure will stay up for some time and, when you switch the ignition on soon after the system was pressurised, the ABS light will only come on briefly as switched by the test device. To check the long ABS light "on", you need to pump the brake pedal (ignition off) some 20+ times then switch the ignition on. Pin 4 of the connector is not ground but ignition switched +12V. Pin 12 (pink wire) is grounded (by the test device, the fluid level switch, the wear sensors etc.) and this lights the Brake Warning bulb up. The pink wire (when not grounded) will show ~12V with the ignition "on" as the ignition switched +12V will flow through the bulb filament and be present on the pink wire. When the pink wire is grounded, the voltage on it will, of course, be zero. If the Brake Warning bulb does not light-up at ignition on with the pink wire grounded, and the bulb is good, then either the +12V from the connector Pin 4 or the ground from the connector Pin 12 is not reaching the bulb base contacts on the PC board. In that case, I would check the PC board traces to the bulb base contacts. The sure way to verify whether everything is good on the PC board is to unplug the instrument panel and, as earlier suggested by Ian, connect a small battery to Pins 4 and 12. Digital voltmeters or ohmmeters sometimes give you false readings.
What did you actually see on the ohmmeter for "shows values"? A good continuity, at the Ohms setting on the multimeter, should show about 1 Ohm or less, usually 0.5-0.8 Ohm.
m. stojanovic, ohm meter showed 0.4-0.7 ohms, jumped around a bit. Now the good news, I was a little frustrated after the troubleshooting, so decided just to let it go and put things back together. There are 2 other plugs underneath the main plug on the brake master cylinder, reset these, put binnacle back together and turned key to the on position, The brake test light illuminated and the ABS light lit. After ABS light extniguished, brake test light went out. Turned key off, tried again, only ABS light on, then extinguished quickly. Left it for an hour or so and tried again. Same result, brake test illuminated, ABS light on, heard pump build pressure, lights out as before. Brake light came on as before. Worked again. Thinking that the 3-4 seconds the brake test light is supposed to illuminate with key in on position only works on mine when ABS pressure is low? Sorry for all the trouble I've caused and really appreciate the help I've received. from fellow f chat members. I guess I jumped the gun on this one, I apologize again.
If you look at the ABS wiring diagram, there is indeed a ABS/brake system pressure input (as well as a fluid level input) into the brake test light. See "201" in the diagram. I recall, however, that the ABS/brake pump is activated when the key is put in position "I". If you are slow to go to position II (ON), the pump will have had time to activate the pressure "ok" switch (201), so no brake warning light in ON. Note that the brake test light needs position II power. The ABS light only needs position I power. However, the brake light should also come on during START (cranking) because of the test module. Did you get the chance to start the engine? No problem, William. I think we all benefitted from this
Im starting the engine today and taking it for a drive. Is the 201 brake system pressure switch in the ABS pump module? I guess it would be? I'll report back on the lights when I crank the engine. nce again thanks for the help.
