Hi, so i am running a AEB engine with APU loom, in a Vw T25 . the APU loom has had the wires added for wideband. Engine runs great, however having issues getting a rpm signal. fairly sure pin 37 from the ecu supplies this. When i ran the AEB loom , i used a small box to convert the signal to use with my clocks. worked great for the time that loom was fitted. currently wired the same pin into the box, but nothing. is this because of the way the signal is delivered, i.e digital rather than analog as the clocks expect to see. any easy eay of changing this ? i've seen that it may be possible to recode in the ecu ?? wiring layout is similar to CE1 as in Mk1 golf. thx
nope afraid not. i only have basic tools multimeter etc propoer buggin me as i like a workign rev counter.
This box you use, does it amplify the signal to create a coil-like spark so the rev counter works? Are you sure you have the right cable from the ECU?
deffo have the right wire. i suspect as the box was used on the AEB engine , perhaps the output is different between the ME3 and ME7 stuff? will have to do some digging, and perhaps purchase a new box thats proven to work with ME7 ecu's.
Depends on what box you have. If it's a signal amplifier to induce the spike the coil makes, the input shouldn't really matter. At least not in the variant I make
its a non descript black box. 4 wires. plus, neg, input and output. seems to be held together with gold glitter glue and may built on a relay. well that's what it like. Perhaps pm me your recommendation, i want a working rev counter as its kinda useful.
Well I would love to sell you one of the ones that I make but I think it's wiser to measure if your (other) parts are doing what they are supposed to. Unfortunately, that can only be done with a scope. If there is no signal, then no box will help.
AEB and APU ecu signals are the same and pin 37 is the correct tacho pin. it is possible the apu ecu doesnt output a signal on the tacho pin, as some later canbus ecu wont but I've only seen this mentioned on US models, but having said that the passat often has more canbus functionality built in which might explain. for example the climatronic module doesnt use the physical pin for rev counter, unlike mk4 which always does. to rule it out try a normal mk4 dbw ecu in there see if you get anything out the rev counter pin
interestingly i'm running a golf wideband unit, with extra pins added for wideband and get nothing i need to check if the pin is actually wired to the loom, it may not be. i did have another pin that i had to manually add, as it wasn't used on the original car.
as long as its a UK/Euro spec MK4 the rev counter pin is active, and is there on the wiring loom even if it is unused. Its needed for the climatronic module as I say, the MK4 one has no canbus connectivity for wideband ecu its pin 37, brown/green
