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1994 900 SE V6 129,000mi. Need help with intermittent check engine light.
History: head gasket repair last fall. Did not replace oxygen sensors at the time. Sensors were original before hg job so they are getting some age. Afterward car ran great but Check Engine Light would come on intermittently at highway speeds. Easing off the gas would cause the CEL to go out. Light has never stayed on constantly. Went to dealer who pulled P0134 "no activity detected” (or more generally, “O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)”). Dealer suggested replacing sensor.
A few months pass, the CEL is still intermittent at highway speeds but more frequent. I replaced front O2 sensor with a Bosch OEM last weekend. Same intermittent CEL at highway speed after job. I wiped the threads with a cloth and the sensor came with a little anti-seize pre-applied. I was very careful with all wires and gently wiped the connectors with a cloth.
Result: exact same CEL intermittent highway speed behavior. What’s going on? Why am I still getting the light? Disconnected the battery yesterday to attempt to clear codes—no effect. My highway mileage is unchanged before and after the job. I can get over 31.5 driving slow (under 60) and around 31 driving about 70.
It’s complicated because I have an OBD-I car and light does not remain lit at all times. I admit that I don’t know _what code_ I'm getting on the highway after the job. I probably need to bite the bullet and hit the dealer for a $32.50 scan where they can tell me the stored codes. Instead, I tried two alternatives: (1) Went to Autozone, but their OBD-2 reader gave a "read error" when we hooked it up. (2) Tried checking the Motronic flash codes when you turn the key on, but I get nothing. See link below. I tried this method both without grounding the pin (just turning the key to on) and also with grounding. No result. Is this because the light is not on constantly?
I would love to buy an OBD-1 reader or computer interface but there doesn't seem to be any such thing for Saab anywhere. I can only find OBD1 readers is for American cars only. Anyone with a 94 or 95 found a solution for pulling odbi codes at home?
My theories:
1. New sensor is faulty
2. Rear sensor now a problem. (No codes for it a couple months ago and the ECU can store multiple codes in history. There was no head gasket leak on the rear cylinders.)
3. Ground problem with sensors?
4. Bad wiring to the front sensor. (I’ve checked all connections thoroughly and was very careful. If it’s in the connection to the main wiring, this is a lost cause. The sensor plugs into a long wire set that goes all the way back into the bulkhead.)
5. Faulty lamda sensor fuse? (Highly unlikely, the fuse looks fine and the behavior is too unusual for this.)
THANKS in advance for any advice, tips, etc on the many questions in this post.
posted by 152.16.68...
http://216.78.172.244/engine_folder/motroniccodes.htm" TARGET="_blank">Motronic flash codes
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