How to use the On-Board Diagnostic (OBD) unit.

Post by **billofdurham** » 27 Nov 2009, 15:27

The 240, 740, 760, 780, 940 and 960 cars from 1989, non-turbo engines only and 1990 to 1995 for both turbo and non-turbo engines were fitted with an On-Board Diagnostic (OBD) unit in the engine compartment. It is mounted behind the left strut assembly and can be used to check for Diagnostic Trouble Codes (DTC), more commonly known as fault codes, in both fuel injection and ignition systems.

This tool is a first step in diagnosing engine problems. Unlike the later models you do not need a scan tool to read the codes.

The first attachment has instructions for using the unit on the 200, 700 and 940 with a list of codes, which may not apply to all models/years. It also contains some further checks to be carried out when certain codes are detected.

NB Erase the codes using the OBD unit. DO NOT disconnect the battery cable until you have checked that the codes have been deleted. If the flash code 1-1-1 is received the codes have been deleted. If the flash code 1-1-1 is not received then disconnect the battery cable to erase the codes. Disconnecting the battery cable will force the computer into a relearn mode which can produce some driveability problems until it has gone through this process. This is something best avoided.

The second attachment has instructions for using the unit on the 960 which has a different different type of ECU.

200; 700; 940 tests with codes.pdf: (1.35 MiB) Downloaded 20255 times

This is an updated list of codes for the 940

Amended 940 DTCs.pdf: (453.56 KiB) Downloaded 4521 times

960 tests with codes.pdf: (842.77 KiB) Downloaded 3863 times

This is an updated list of codes for the 960.

960 Fault code list.pdf: (3.66 MiB) Downloaded 2925 times

Bill.

bright · Post by **bright** » 13 Dec 2009, 23:34

I really wish that I had a 96 960 than a 95. There are a lot of good reasons, but one of my favorites is that they are OBDII compliant. It's just so easy to get them to spill their guts.

Post by **mdm+mfm** » 28 Feb 2010, 16:12

Hello Bill,

I am new to this forum and wanted to say thank you for the posted information. Being new to this unit on my '92 245, it has been very useful. I do have one question though: in the attachment at the bottom of the trouble codes under fuel system fault codes table, there is a reference made to "See I - SYSTEM/COMPONENT TESTS article". Being that I am having problems interpreting how to address some of my codes, I wanted to inquire where I might find this article. Any help would be greatly appreciated. Thank you in advance, and have a nice day.

Matt

Post by **billofdurham** » 01 Mar 2010, 12:39

Matt,

That is a large document which would take up a lot of space on the forum.

Post your codes in the main part of the forum and I shall post the appropriate parts of the SYSTEM/COMPONENT TESTS.

Bill.

Post by **mdm+mfm** » 01 Mar 2010, 18:29

Thank you Bill!

Kirby J · Post by **Kirby J** » 20 Apr 2010, 21:21

I have a 93 940 NA. Rex/Regina. In the location you described I found a small galvanized box with an electrical connector and one vacuum line from the throttle body. I opened the box, and found a sealed electronic unit with "GM" identification, but no OBD unit. Am I looking in the wrong place, or does my car not have an OBD connection.

Post by **billofdurham** » 21 Apr 2010, 12:34

The Regina system does have OBD and my books show it to be in the same place as for the other systems.

Bill.

Kirby J · Post by **Kirby J** » 22 Apr 2010, 13:01

When you say "behind the Left strut" Do you mean between the strut and the windshield, or between the strut and the radiator.
Semantics can be a real problem sometimes. I did see two covered connections just forward of the strut. Each of them have a factory seal, like a zip tie, securing them.

Post by **billofdurham** » 22 Apr 2010, 15:48

Unfortunately we don't have the Regina system in the UK so I have never worked on one. The OBD unit has a lid on it to keep out dirt and water and is shown in its closed state on the left of the attached:

940 OBD unit.pdf: (150.95 KiB) Downloaded 2204 times

Bill.

Kirby J · Post by **Kirby J** » 22 Apr 2010, 21:30

Thanks, will look for it tommorrow