Hi kittysgrayvolvo,

Thank you for very much for your comprehensive response to my diagnostic error code issue - lots of information in your reply.

Once again I finally got the opportunity to work on my 1989 Volvo GL. Following the directions in my 1989 Volvo Service Manual (image attached). I removed the connector from the control unit and started to check a variety of voltages and ground connections on the control unit connector - they all passed until I got up to the throttle switch tests.

When I connected the ohmmeter between ground and the number 3 connection on the control unit connector the ohm meter indicated an infinite resistance - that is what it was supposed to be. I then proceeded to the press the gas pedal all the way and should have received a zero on reading indicating the ground connection was intact - I got once again and infinite reading on my own meter indicating there was a grounding issue. I check the ground connection at the intake manifold and found it to be intact and at this point I was confused. Before further testing on the ECU connector I decided to reinstall the connector on the ECU and try to find the problem with the ground on the throttle switch.

I then went to Control Function 2 on the diagnostic system and proceeded to test throttle switch. My manual differs from yours all tests except the EGR are done in socket 2 .I turned the throttle control to the full load position and pressed the button on the diagnostic socket twice and the diode began to flash like it was supposed to. I released the throttle control and the diode flashed a series of 3-3-3. Following the instructions in the Volvo Service Manual I turned the throttle slightly it was supposed to flash 3-3-2 it did not. That was consistent with the reading I got on the ECU connector – ground problem?

Following the instructions in the service manual once again I checked the throttle switch setting and listened for a click when I turned the throttle slightly that click was there. I adjusted the link arms with a feeler gauge between the throttle lever on the adjustment merit screw should be about 1 mm. By this time it was getting dark and I decided to quit for the day. When I read the diagnostic setting for some reason came up 1-1-1. I hadn’t reset diagnostics it but accepted the 1-1-1 reading and proceeded to start the engine fully expecting the check engine light to illuminate as it had in the recent past – it didn’t. Very confused at this time and not very confident the check engine light will remain off.

Kittysgreyvolvo I’ll respond to the questions you asked in the very near future. The information you supplied in your response with take me some time to read and “digest” but I do know the answers to most of your questions.

Thank you once again for taking the time to respond to my diagnostic code issue and your knowledge and experience with Volvo issues

Wallym

Cropped image of my Volvo Ser4vice Manual Cover:
https://www.brickboard.com/GALLERY/images/12644.jpg