So in this weeks episode, we examine and repair the dreaded slow down light. These are controlled by the ECU, which gets a signal from the cat converter thermocoupler control module. Jodi's started to flash the slow down light. I knew what it was, and didnt worry about it, as I knew the CATS werent overheating. BUT, one day, the light light started flashing, then stayed on solid, then one bank shut down. So, I tried to find some information, but there is **** all available, so that left me with just working out the system. Pretty basic really so I won't prattle on too long about it. The Motronic ECU that controls the slow down light looks for a varying 5v signal from the Cat control module. The higher the voltage, the hotter the thermocouple probe is getting. Generally you will see about 2.4v at the thermocouple probe. The Engine ECU will start the light flashing once the output voltage from the cat control module (CCM) reaches 3.6v the light will start to flash. At 3.8v the light will come on and stay on solid, and at 4v, the engine will cut out the effected bank and leave you running on 6 cyls. I tested the thermocouplers and found one to be shorted. Replaced both of them from Eurospares and bingo. BUT, as I was checking the CCM's, I noticed that when I pushed on the thermocoupler connector on the passenger side, the output voltage would go up to 5v. So I have a stuffed CCM as well. Replaced it with a second hand one I sourced to MJ to confirm, and all good. For any of you with these systems, I have found a place in New Zealand that manufactures new units, with better electronics and hardware. They are called Technistrada. Much cheaper and better than the factory units.
So, translating that, you got the widget, monkeyed with it a bit, then had to fiddle with it, and now it works. Oh, and you can save yourself a lot of trouble and get a wudget from NZ
Well, I WAS going to go into the N x 120 sec algorithm Ferrari uses for it, which I managed to find in the workshop manual, and how the voltages correlate with this, but I figured you balloon heads would need the Benny Hill music in the background to understand it!
So, today was engine service, gearbox service, rear wheel hubs/bearings removed and re-packed and of course something electrical. The ABS light stayed on once I’d refitted the RHR hub assy. I figured it was the wheel speed sensor, so I checked it and it was open circuit. Checked the LHR and it approx. 1.1k ohm. Quickly found a Bosch wheel speed sensor which looked pretty close, and these are NLA. A slight modification to make it fit. The sensor is the correct thing diameter but has a raised lip at the base which needs to be filed down. It took about 2 mins. It fits perfectly but requires a 1mm fibre washer to get the required 1mm gap from the tome wheel. Changed the harness plug to a waterproof deutsch plug and it was good to go. I guess this sensor will suit more than the 456 so here is a pic of the part no. Image Unavailable, Please Login Sent from my iPhone using Tapatalk
Bosch part no. 0 265 006 228 It’s resistance is 1.7k ohm. The frequency obviously isn’t an issue, but I thought the amplitude may have been. These old systems are pretty rudimentary and it made no difference. It works perfectly. Sent from my iPhone using Tapatalk
Oh, and I balanced the throttles. It’s surprising the difference it made. Sent from my iPhone using Tapatalk
