CEL 9, Cylinder Position Sensor Check Engine Light

Tiny
SMCMULLIN33
  • MEMBER
  • 1990 HONDA PRELUDE
  • 2.1L
  • 4 CYL
  • FWD
  • MANUAL
  • 189,000 MILES
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 am at a loss at this point after trying a new sensor, new ecu and checking the wire. Does anyone have any further suggestions? Most suggestions I have seen say to replace the distributor, but unlike most Hondas of this year, the Cylinder Position Sensor is not located in the distributor.
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Tuesday, June 3rd, 2014 AT 1:18 PM

9 Replies

Tiny
HMAC300
  • EXPERT
Check for a short between orange and white wires I assume you have pulled the clock fuse for 10 seconds to reset the ecu but you really need a test harness to test this out correctly
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Wednesday, June 4th, 2014 AT 7:09 AM
Tiny
SMCMULLIN33
  • MEMBER
I have checked the wiring, tested the resistance at the ecu plug and just in case took it a step further and ran new wiring last night, no change. And I've just been disconnecting the battery, not pulling the fuse.
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Wednesday, June 4th, 2014 AT 7:17 AM
Tiny
HMAC300
  • EXPERT
Check for ground between each terminal if it exists the sensor is bad should be 700-1000 ohms as well otherwise I have no idea what to tell you if you have replaced everything and still getting code.
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Wednesday, June 4th, 2014 AT 7:31 AM
Tiny
SMCMULLIN33
  • MEMBER
I've checked for continuity at both terminals and there is none and the sensor is measuring at 961 ohms. I'm completely stumped at this point. My original sensor measured almost exactly the same. When it first came on I was driving down the freeway, the car stuttered and the was an audible thump from the engine bay, but everything froma mechanical standpoint seems perfect.
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Wednesday, June 4th, 2014 AT 7:39 AM
Tiny
SMCMULLIN33
  • MEMBER
To clarify I had to get a used sensor because it is discontinued and unavailable new from everywhere I have contacted, but according to the FSM both sensors are within specs.
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Wednesday, June 4th, 2014 AT 7:43 AM
Tiny
HMAC300
  • EXPERT
Don't know what to tell you try pulling the clock fuse see if it changes anything probably won't check your grounds too one going to pcm an d theother going to engine from battery and battery to body.
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Wednesday, June 4th, 2014 AT 7:46 AM
Tiny
SMCMULLIN33
  • MEMBER
Will do when I get off work, thank you for the suggestion. This is turning intoa nightmare to troubleshoot.
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Wednesday, June 4th, 2014 AT 7:52 AM
Tiny
SMCMULLIN33
  • MEMBER
Ok, 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.
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Friday, June 13th, 2014 AT 8:59 PM
Tiny
HMAC300
  • EXPERT
Try cleaning the ground from battery to body and battery to engine maybe that will take care of it unless there is an update that isn't around. Other than that I'm at a loss
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Saturday, June 14th, 2014 AT 11:49 AM

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