Ryan62586

I have a 1995 Honda Civic DX (D15B7) It's reading a CYP sensor fault code. I have tested the CYP sensor with an ohm meter and its reading 386. the Manual says it needs to be between 350-700, so to my knowledge it is still good, correct?. I have ALSO checked the wiring from the ECM to the Ignition Harness (beside the distributor) with a Continuity tester, and the wiring is also good. So the only thing now I can think of is either a bad ECM maybe, or Distributor a little out of time? Also the car runs smooth. and the CYP code never goes away. .. ANY help is greatly appreciated!! Thanks in advance!

ezone

Code 9?
You checked resistance of the sensor. It apparently passed the test. That doesn't necessarily mean it is good, it only means that it passed that particular test. Example: If the pointy thing on the trigger wheel that makes the sensor generate its signal was completely missing from the distributor, the sensor would still pass its resistance test. It just wouldn't generate its signal, ever.
If the gap between the sensor and the trigger wheel was too big, the signal would be weaker than what the ECM needs to see, or nonexistent.
See what I mean?

Did you check resistance between each wire and ground?

Next step is to disconnect the ECM and check for the same resistance at its terminals B11 and B12. Also make sure there is no continuity to ground.

Got a labscope? That is the best way to see the sensor actually operate.

Most of the time when I saw them on a regular basis, the problem was the distributor. I can't say that definitively though.

Ryan62586

Yeah I understand. But if the CYP sensor was truly bad, would it not run bad? I mean, the car purrs like a kitten. Tried resetting the CEL and it still came up (Code 9)

ezone

IIRC, the CYP is used for fuel injector synchronizing, so the engine wouldn't run horribly bad when the ECM loses the CYP sensor input, it will still run decently but not ideally. The injectors revert back to batch firing instead of sequential firing. (If I am right, I can't find any documentation on this.)

Did you compare the CYP pickup resistance to the other 2 pickups in the distributor?

Are you removing the backup fuse to clear codes?

Does the code return immediately without having to run the engine, or do you have to run the engine to get the code to return?
I'm curious about this, and if the code resets without running the engine--will the ECM also set codes for the other two distributor sensors if the distributor harness is unplugged?

Got any friends? Get a test distributor (or a test ECM) from a known good running car? We have 4 or 5 different used test distributors at the shop just to make diags quicker.

Have you done the resistance check at the ECM connector? Do the check there, and leave the meter connected to it. Go out in the engine compartment and start wiggling harnesses while watching the meter, see if the reading changes at all.
The only other connector that carries the distributor wiring is in the set of harness connectors on the passengers strut tower, 10 terminal gray connector.

Also, I see people try to jam meter test probes into connector terminals and spread them out so they can't make a good connection anymore. (This is a real PITA to repair!!!) So the sensor and ECM could be perfectly good but have crappy connections....
Always backprobe a female connector to take readings when possible, and when you don't have the correct terminal to plug in from the front side..

Ryan62586

Thanks for the reply. It's boggling my mind, I printed this out so I can try all of this. I'll reply when and if I find the culprit lol