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Should I diagnose or just replace rear O2 sensor? Posted by sam96CS [Email] (#852) [Profile/Gallery] (more from sam96CS) on Wed, 22 Aug 2012 15:48:23 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I can get a new Walker 250-24134 for $77 (nothing to splice), and it looks like the rear O2 sensor is less of a pain to replace than the front.
Symptoms and clues: '96 9000 CS fpt 185K miles with front and rear O2 sensors. No CELs, but in over a year of all kinds of driving the OBD2 catalyst monitor hasn't run. Spark plugs look normal, and because fuel mixture decision are based on front sensor input I think the front sensor is OK. From what I've read here and in the T5Suite documentation the rear sensor is used mainly to verify that the Cat is doing its job. But it can't do that if the catalyst monitor never gets ready.
From an old Ari post I think the rear sensor's signal goes to pin 23 of the ECU, but I don't know how much voltage is normal or how much variability in the signal is acceptable.
I know it's generally better to diagnose rather than throw money at parts, but I'm tempted to take a chance on this one. What do you think? Is there a practical way to test the rear sensor other than sticking in a new one and seeing what happens?
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