Follow up to use of Harrison R&D OBD-II scanner.[900/1996]

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Follow up to use of Harrison R&D OBD-II scanner.[900/1996] posted by Jim Bowers on
Monday, 20 August 2001, at 3:52 p.m.

I'm back from vacation so I'm in front of the fast "work" internet connection to post the results. The inexpensive, $140 for the Palm version, generic smart cable & software from Harrison R&D helped me diagnose and replace the rear O2 sensor!

The "check engine" light on my '96 965 with the OBD-II system had been comming on, but only after longer trips.

After a couple false starts using the scanner system with my Palm Pilot I borrowed my son's laptop to see if the Palm SW was preventing me from seeing the DTC.

After much experimenting and general "trying things" I learned that the default CPU that responds to the Harrison system on the Volvo OBD-II bus is NOT the Engine Control Module, ECM! I discovered that if you haven't "switched CPUs" in the last few seconds the bus reverts to the default NOT ECM CPU so the query for the DTC goes to the wrong CPU (Transmission I think). I finally got the DTC, P0136, by issuing a command to switch CPUs and as soon as the response indicated I was talking to the ECM I issued the retrieve DTC command and Volia! there it was. The manual says the P0136 code message is Rear heated oxygen sensor signal is missing/faulty. I couldn't find any problems with the wiring or connectors so I ordered a new sensor. $180 with VCOA discount.

On Friday night 8/3/01 I replaced the rear sensor because on Saturday morning we were taking a 150 mile trip to my nephew's wedding in Vermont and I wanted to see if the fix was real. I've driven the car almost a thousand miles since and the fix is real. The car is now getting over 22 MPG at 75 MPH and the idle is smoother. --
Jim Bowers, North of Boston, '96 965 with 84K, Had '85 745 Turbo diesel for 200K

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