Well That Escalated Quickly

[tiger_e30]

Anyone know what voltage the ecu supplies to the o2 heater relay? Trying to figure out where to wire pin 23

[jeenyus]

The oxygen sensor heater circuit should have 12 V between terminals 4(+) and 3(-) at the harness side of oxygen sensor connector (the pin side) with the ignition on.

[tiger_e30]

The oxygen sensor heater circuit should have 12 V between terminals 4(+) and 3(-) at the harness side of oxygen sensor connector (the pin side) with the ignition on.

Nope the megasquirt isn't putting voltage to the relay

[tyeler18]

Nope the megasquirt isn't putting voltage to the relay

Most computers ground the o2 control relay. Should have battery feed to the relay, and the computer controls the ground.

[tiger_e30]

Most computers ground the o2 control relay. Should have battery feed to the relay, and the computer controls the ground.

Thank you that makes sense. The Bentley and electrical trouble shooting book don't actually have any diagrams of the motronic and relay circuits. Going to jump it to ground and make sure that works then figure out what to jumper on the board

[tiger_e30]

Most computers ground the o2 control relay. Should have battery feed to the relay, and the computer controls the ground.

Connected pin 23 to ground on the proto area and it works! Next up figure out if its controlling idle correctly and why the motherboard tach output is wrong

[tiger_e30]

The machine shop took off the crankshaft 3 in 1 pully and harmonic balancer as one piece. On reinstall aby reason to not just slide the entire assembly on and use the 22mm bolt to tighten everything?

[tiger_e30]

The machine shop took off the crankshaft 3 in 1 pully and harmonic balancer as one piece. On reinstall aby reason to not just slide the entire assembly on and use the 22mm bolt to tighten everything?

To answer my own question can't see the mark on the harmonic balancer to line up with the timing cover when the the whole thing is a assembly