CYP sensor code 9 problem

[wagon-r]

I am getting a code 9 for the CYP sensor and I can't get it to go away. I am hoping the experts here can offer me some advice.

The original problem was that the CYP sensor in my 1997 F22B1 Accord distributor is incompatible with OBD1 ECUs. Thus, my OBD1 P72 ECU threw a code 9 with my 1997 F22B1 distributor, even though there were no codes with the 1997 ECU.

To fix this, I installed a 1991 Accord distributor (1990-1 distributors had an internal coil, as did my F22B1 distributor, but 1992-3 and F22B2 distributors used an external coil). I created a custom wire harness from the 1991 distributor to the 5-pin distributor connector on the 1997 Accord wiring harness for the F22B1.

I only rewired the 5 pins from the 1991 distributor: CYP +/-, ECU signal, power, and tach output. The OBD1 ECU seemed happy with the CKP/TDC signals from my crankshaft position sensor and did not throw any codes, so I did not wire up the CKP/TDC signals from the 1991 distributor.

I installed the 1991 distributor and the MIL turned off - for a couple minutes. Then the code 9 came back. It now comes back almost immediately after I clear it. The engine runs exactly the same way as it did with the 1997 distributor (some minor stumbles during warmup around 2000 rpm, otherwise runs fine).

So, I got out the manual and did the diagnostic checks. Over the last 2 days I checked the resistance across the CYP sensor three times - at the ECU pins - and it read between 375 and 450 ohms each time. Spec is 350 to 700 ohms, so this should be fine (my F22B1 distributor had resistance of 787 ohms across the CYP sensor). I also checked continuity between the CYP pins at the ECU and ground and this was fine as well.

So, I'm stumped. Is is possible that the distributor could pass the diagnostic checks and still be bad? Should I try a third distributor?

Or, how likely is it that the ECU could be defective? Outside of this, the ECU seems to be working fine. Also, PureTuning in Toledo chipped my ECU and installed a Hondata S300 and he was pretty picky - he rejected the first ECU I bought because he didn't like the soldering on a few pins and made me buy another one.

[cp[mike]]

i wonder if this is a case of other factors affecting it. YES, at rest, it's wired correctly - but are those wires running close to any other wires? anything making electrical noise? power wires? it might be getting signal just fine, but that signal might come in erratically, throwing the code for inconsistency rather than connectivity in general.

this sort of stuff is usually more of a problem with custom-wired stuff. high-rate pulse signals from the distributor, and the o2 sensor too, when people make extension harnesses. Maybe your wiring connections/routing/length is the reason...

just something to think about and investigate, at least.

[wagon-r]

I hadn't thought of that. Except for the distributor adapter my wiring harness is completely stock, but I did just wrap up the unused CKP/TDC wires next to the CYP wires from the distributor. I'll pull them out tomorrow and make sure they are well separated and see if that makes any difference.

[wagon-r]

Well, I pulled the extra wires for the TDC/CKP sensors out and isolated them from the wires I am using. It made no different - I still immediately get the code 9.

Any other suggestions? Can the distributor still be bad if it passes the diagnostics in the manual? It is time to replace with a "known good ECU" and see if I still get the code 9? (Problem here is that, unless I want to buy another ECU - and I've already bought two - I'm not sure where to find a known good ECU.)

[wagon-r]

Finally fixed!!!! After swapping in three OBD1 distributors, including a new one, another OBD 1 ECU to see if it eliminated the code 9 (it didn't), and revising wiring several times, I finally figured out what was going on with the Code 9. It turns out that the ECU must be checking the timing of the signals from the CYP, TDC, and CKP sensors.

I am still using the TDC and CKP signals from the crankshaft sensors on my 1997 Accord. When I swapped in the OBD 1 distributors, I installed them so they were in the middle of the adjustment range. The position of the distributor doesn't affect ignition timing (which I verified with a timing light), as this is from the crankshaft sensors. But it does affect the synchronization of the CYP versus TDC/CKP sensor signals. It finally occurred to me today that the ECU might be checking the synchronization of the signals, so I retarded the distributor - viola! Problem solved.

So, I feel kind of stupid. I spent a lot of time and some money troubleshooting distributors and ECU, revising wiring, and buying distributors. All I needed to do was rotate the distributor.

Bottom line - if anyone is using an S300 in a 1994-97 Accord EX, you need to:
- Buy a 1990-91 Accord distributor (internal coil like the 1994-97)
- Rewire the distributor signals to the engine harness (I didn't bother changing the TDC/CKP wiring from the crankshaft sensors to the distributor sensors)
- If you get a code 9, rotate the 1990-91 distributor to eliminate.

I think the distributor in the 1994-97 Accord LX is compatible with the S300, so you don't need to do this if you are starting with an LX.