I know that there are not many of us out there, since they made less than 200 non-SE cars in early 1989 but if one person finds this useful then my life has meaning. :nerd:
The '89 non-SE cars have a different ECU from later cars, we have the 3 connector ECU which was used on some Chevy's and some other GM cars. The ECU is easy to find and runs about $125 or so. I recently began a few different projects on my car and one of them was planning out the install of a Rostra cruise control. Now Rostra offers several different ways to generate a speed signal if you don't have an ECU or if you have one but do not appear to have a speed signal output. That was the case with my car. The ECU map shows two inputs from the wheel sensor, but no output signal and therefore no pin assigned to that function. To use a cruise control you must, obviously, have a speed signal so the control has an input to work with. And while you can approach this problem in different ways, the easiest solution is to have an ECU which generates a speed signal in pulses-per-mile so you can simply hook up the Rostra to that output and not have to invest in any other hardware.
I found on-line a pin map for the '89 ECU which is in my car on a GM hot rod site. And it shows that connector 2 (the middle one) has a speed signal output at pin B11. So I wanted to see if my car, indeed, has such an output. The EMG manual shows a pin manual and C2B11 is shown as empty and the Lotus #2 ECU connector harness has no wire lead for the pin at the B11 address.
So I added a pin to C2B11. The GM manual says with the key on that pin should show about 4.9V relative to ground and that with the engine running it should be a little above 5v. So, I put my multimeter on the pin output wire and got zero voltage in any key position. So what did I do? I called Sanj, electrical wizard and confidante, hand-holder during scary projects, and frequent patient listener to my queries about "how come the car does ---------?".
Sanj thought about it and said it may require a "call-up" voltage to operate. There are ECU functions which require a reference voltage which must be applied to the pin in order for the ECU to operationalize the pin function. So I located a 5v source and applied it to the C2B11 pin lead and I got 4.9v with the key in the "on" position and 5.2v with the engine running. So then I raised the right rear wheel off the ground (this is where the magnetic sensor is mounted), put the key in the on position and started to spin the wheel. Viola! speed signal output.
So, that's what you'll need to do if you want a speed signal from your pre-SE ECU! Thank you Sanj! You are a hero to me :clap:
Now I am saving my pennies for a Rostra.
Tom
The '89 non-SE cars have a different ECU from later cars, we have the 3 connector ECU which was used on some Chevy's and some other GM cars. The ECU is easy to find and runs about $125 or so. I recently began a few different projects on my car and one of them was planning out the install of a Rostra cruise control. Now Rostra offers several different ways to generate a speed signal if you don't have an ECU or if you have one but do not appear to have a speed signal output. That was the case with my car. The ECU map shows two inputs from the wheel sensor, but no output signal and therefore no pin assigned to that function. To use a cruise control you must, obviously, have a speed signal so the control has an input to work with. And while you can approach this problem in different ways, the easiest solution is to have an ECU which generates a speed signal in pulses-per-mile so you can simply hook up the Rostra to that output and not have to invest in any other hardware.
I found on-line a pin map for the '89 ECU which is in my car on a GM hot rod site. And it shows that connector 2 (the middle one) has a speed signal output at pin B11. So I wanted to see if my car, indeed, has such an output. The EMG manual shows a pin manual and C2B11 is shown as empty and the Lotus #2 ECU connector harness has no wire lead for the pin at the B11 address.
So I added a pin to C2B11. The GM manual says with the key on that pin should show about 4.9V relative to ground and that with the engine running it should be a little above 5v. So, I put my multimeter on the pin output wire and got zero voltage in any key position. So what did I do? I called Sanj, electrical wizard and confidante, hand-holder during scary projects, and frequent patient listener to my queries about "how come the car does ---------?".
Sanj thought about it and said it may require a "call-up" voltage to operate. There are ECU functions which require a reference voltage which must be applied to the pin in order for the ECU to operationalize the pin function. So I located a 5v source and applied it to the C2B11 pin lead and I got 4.9v with the key in the "on" position and 5.2v with the engine running. So then I raised the right rear wheel off the ground (this is where the magnetic sensor is mounted), put the key in the on position and started to spin the wheel. Viola! speed signal output.
So, that's what you'll need to do if you want a speed signal from your pre-SE ECU! Thank you Sanj! You are a hero to me :clap:
Now I am saving my pennies for a Rostra.
Tom