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Red Brick? Got an old Snap on MT2500? It is a very capable scan tool, especially on the older stuff…
The O2 sensor can very well keep it from going into closed loop. I recommend diagnosing if it is a bad 02 and replace it if necessary.
Cheers!
-Karl
Its pretty simple… That is an old unheated O2 sensor (not powered). I am surmising this is a single wire version… Just backprobe the wire with the positive and put the negative DVOM probe on a good ground (set on DC volts)…. If your results are the same as the MT2500 then chances are it is the O2 sensor…
-Karl
One other thing to keep in mind is that those single wire O2s can lose enough heat in an idle condition that they’ll stop working and that will throw the engine back into open loop. Get the engine up to running temperature and then hold your throttle to 1500-2000 RPM at idle or just monitor the O2 sensor PID while you’re driving. Then you’ve got getter reason to suspect an O2 problem.
If you still don’t have a signal change in those conditions, Then you can use a test light to test the O2 circuit. Attach the test light to battery (+) and then probe the connector for the O2. Watching your O2 PID, it should shoot the voltage high. It will probably show you a max value of 1.250 or something to that effect, which is good enough.
Update on the O2 sensor it seemed hard to remove but I got it out in under 20 minutes. Wd-40 and a harbor freight swivel end ratchet on a O2 sensor socket got it out no problem. It does now go into closed loop
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