Question: Speedometer with aftermarket ECU

[spinos82]

Hey! Im tuning my corvette and ive changed the ecu to Autronic SM4, got everything but the speedometer and tachometer to work. But the main question is the speedometer, what should I be looking for ? I figure there should some wiring harness to cut in on So throw me a picture or something that can help along the way and it would be great.

 

[vetteoz]

what should I be looking for ? I figure there should some wiring harness to cut in on

Without INFO about how you connected the new ECM , have no idea of what you have done / disconnected / removed
to make it work.Most on here would not be familiar with the unit or it's wiring

Tacho feed is wire direct from HEI (coil- ) to tacho ( white wire ) so easy fix if you have disconnected it.

Speedo in '88 goes from VSS to dash then to stock ECM so should still be operation UNLESS you have disconnected related wiring

does the Autronic require a speed input?
how are you doing it if it does ?

 

[spinos82]

Hey, thnx for answering. Im kinda new at tuning, but a little help might be all i need. Autronic says SM4 pin 12 output8/ tacho blk/gry. So should it be like this. white wire to HEI from HEI to coil- and the SM4 cabel? or am I lost

Sounds like the speedo should work by itself, dont think ive touched anything with it. The car hasnt been running for 6years now so might be some damaged part like the vss. But im gonna check the cables from the vss also, might be that ive cut them

I dont think the Autronic requires a speed input, I just had no idea how it worked with the speedo, only had the car 1 year.