Just finished tII swap. How can I tell if the ECU is fried in my s4 tII ECU? My secondaries are failing, I'm getting TOTAL power loss at ~3800-4000 rpm like i hit a wall. I checked continuity from the injector plugs to the ECU and on all 8 wires and they checked fine. Also checked for shorts... none. BTW new injectors and to make sure all 4 worked i swapped what were the primaries for the secondaries and the car started right up, but still hit a wall when driving around. Perhaps the ECU is fine, if so anyone have any ideas?

 

Did you check for 12vdc at the ECU? At the secondary wires? Key to ON?

 

Sounds more like a pressure sensor/possible wiring problem.

 

That's a thought. Turn the key to ON. Backprobe pin 2B on the middle ECU plug. It should show no more than maybe couple of volts. IF it shows batt voltage of 12vdc or so..........mis wired EM harness.

Or you could check this at the boost sensor itself. Unbolt it and turn it's body with the elec plug facing upwards for access. Key to ON, Engine OFF. IF you read 12vdc on the BROWN/RED wire........miswired EM harness.

Which EM harness did you use? A JDM? A USA turbo? Or the original non turbo EM harness?

 

ill try everything you two just suggested when i get home. to answer your question Hailers yes it's the stock wiring harness for the s4 turbo engine. no after market stuff here, just direct change over from the turbo parts car..original 20 year old wiring harness

 

i am having the same problem with my 87 TII 3500 is like hitting a brick wall but this is only under boost no prolems when not boosting

 

Using the stock turbo EM harness in conjunction with the non turbo Front harness causes problems because some of the pinouts from the turbo EM harnesss to the non turbo Front harness are not the same.

It's not a big deal IF some small changes are made.

One of the consequences of using a turbo EM harness on non turbo Front harness is you end up feeding a constart 12vdc to the pin 2B on the ECU which is the input to the ECU from the Boost sensor. Usually that pin 2B only sees maybe three volts dc.

I'm talking series four cars here not series five which is different. Only series four.

So if yours is a series five............disregard what I wrote above.

Pin 2B is on the bottom row, far right. A brown wire with Red stripe. Middle plug.

 

i got 2.31 volts on 2b

 

That's pretty normal. So much for my guess.

Have you had all the electrical plugs connected up everywhere, and then gone to pins 3F and 3H and with the key to ON, see if there is batt voltage there???

IF you have or do, then maybe consider extending the wires of the meter to one of those plugs, turn the meter to vdc and go for a ride. When under load and over 3800rpm the voltage shown prior to that, should drop off significantly. Say it was 12plus volts prior to 3800, now it should drop to maybe severn volts.

How big the voltage drop depends on how hard you pressing the pedal.

Actually you can do this to some extent in your driveway. Disconnect the vacuum line to the boost sensor and plug it off so it does not cause a vacuum leak. Then start the engine and rev it above 3800rpm. When you hit 3800 I guarantee the engine will bogg/act funny but it you keep reving it'll smooth out a little.

While doing that, look at your meter that is backprobing pin 3F or 3H. The voltage should drop *some*. How much? Not as much as if you were actually driving, but it should drop some, proving the secondarys are coming online.