CEL 9, Cylinder Position Sensor Check Engine Light

1990 HONDA PRELUDE
2.1L • 4 CYL • MANUAL
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SMCMULLIN33
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I have a 1990 Honda Prelude Si with a B21A1 engine. I recently had the engine light come on and it is showing 9 flashes, or the Cylinder Position Sensor. I have checked the resistance of the sensor and it came back within specs, according to the Factory Service Manual. I have run all diagnostic procedures according to the FSM, checking resistance of the sensor directly at the sensor and at the end of the wiring at the ECU, all checked out within specs. I have tried a different sensor and also a different ECU, and the CEL is still coming up. I have checked to make sure that the crank to cam timing is set correctly. The engine was recently rebuilt and all was running fine, the only work I had done right before the light came on was replaced the alternator. I got my hands on a test harness and found that there is continuity when checking the wiring at the ecu test harness like the manual say, now my issue is a ran new wiring and the continuity and problems are still there. Why do I still have continuity at the body when testing at the harness and not at the sensor itself. This tells me it should be wiring but I replaced both wires and now change. Thank you for anyone who can help me.
Jun 13, 2014 at 9:14 PM
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SMCMULLIN33
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I missed the part about not plugging test harness into the ecu, there is no continuity but the cel is still coming on. Im lost and don't want to just throw parts at this thing.
Jun 13, 2014 at 10:00 PM
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KHLOW2008
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Seems weird that the CEL is coming on even when wiring and sensors have been replaced. At the thermostat housing, check and ensure the ground circuit is clean and secure.

What are the resistance for the original sensor and the replacement sensor?
Jun 14, 2014 at 10:59 AM
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SMCMULLIN33
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955 and 946. I've already checked and cleaned this ground.
Jun 14, 2014 at 11:36 AM
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SMCMULLIN33
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Any other advice?
Jun 15, 2014 at 1:30 AM
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KHLOW2008
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Does the CEL come on immediately or after some running of the engine?
Jun 16, 2014 at 8:21 AM
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SMCMULLIN33
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Comes on after about 5-10 seconds.
Jun 16, 2014 at 11:38 AM
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KHLOW2008
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Sorry for the delay in replying. Is the replacement sensor new or used?
You mentioned checking the camshaft timing, how sure are you that both camshafts are timed correctly?
Jun 26, 2014 at 11:27 AM
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SMCMULLIN33
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I re did the timing as it was a tooth off, it's correct now. The sensor I'm using is used, the part is no longer available new. But both sensors test correct.
Jun 26, 2014 at 11:33 AM
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KHLOW2008
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After redoing the timing, the problem is still there?
Jun 26, 2014 at 11:44 AM
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SMCMULLIN33
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Yes
Jun 26, 2014 at 11:51 AM
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KHLOW2008
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Did you open the sensor cap to check if there are any contamination internally?
Jun 26, 2014 at 12:42 PM
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SMCMULLIN33
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Yes I did, it is clean and rust free inside and both wires look good. I'm curious, could the distributor cause this on this motor at all? I know the sensors in the distributor help to sync with the CPS.
Jun 26, 2014 at 12:54 PM
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KHLOW2008
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It is possible the distributor is related. Did you test/check the other 2 sensors? Distributor would normally throw a Code 4 or 8
Jun 26, 2014 at 1:41 PM
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SMCMULLIN33
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I did but the distributor looks bad inside, both sensors did test good though. It is only throwing a code 9.
Jun 26, 2014 at 1:45 PM
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KHLOW2008
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Sorry for not being able to help you. I have gone through everything and could not find anything that I could add in based on what you have done. Hope you can get the problem resolved. Good luck.
Jul 17, 2014 at 6:50 AM