I have had a persistent code 9 (#1 Cylinder Position CYP Sensor Fault). This sensor is in the distributor.

Long story here. Several years ago, this code first appeared. I purchased a replacement distributor and problem was fixed for a long time, until this past summer, when problem reappeared (Code 9). Symptoms are rough starting, difficult start particulary on wet damp conditions. Once warmed and running, the symptoms disappear and CEL will not come on when started.

I now suspected a wiring fault, but checked sensor (good), and checked sensor from ECU connector in cabin, again good.

Not believing my ECU could be bad, I bought another distributor and again the problem seemed cured for a short time, but has again appeared after not using car for several days (now a spare to drive when I'm repairing something else).

I now believe my ECU must be intermittent w/ a cracked circuit or component.

My question: Does anybody see another possible fault I could investigate or diagnostic to perform?

Thanks

 

Hey T.H. is that on the 1994 or the 2007 Accord...?

 

It's the 94 EX.

Fault is constant now. It makes it difficult to crank, but will crank and run decently. Code disappears when ignition is cut off and does not come back until you start again, i.e w/ switch in On position there is no CEL.

thanks

 

Now that the problem is constant, you should try rechecking the resistance at the sensor and at the ECU.

If the resistance checks out, the circuit problem could be simple as bad solder joints like the MFR typically has. The problem is that solder joint are small on those board, so a soldering iron will not work.

What I would do is remove the ECU and heat it with a heat gun (a glorified hair dryer). A hair dryer may get hot enough to remelt the solder. I brought back my brother's laptop video processor and several hp printer network cards by heating up the board.

 

That's my plan today. Check resistances at ECU and again at distributor, if the values at ECU show out of spec. If all OK, I'm going to pull the ECU out and try to find a replacement. A used ECU should be $50-$100.

I used to think Honda ECU's were bullet proof and they are very reliable. However I had a fault on my ECU board on Acura 2.5 TL this year. A capacitor leaked and corroded the board circuit film. I tried a repair, but soldering on these very fine boards requires some very fine tools which I don't have. Besides, I found a replacement for $35.

thanks

 

I pulled the ECU module out and inspected circuit board carefully. It looks pristine, like the day it rolled off the factory line. No hint of damaged components anywhere. I looked at both sides w/ same results.

I checked the resistance of the CYP sensor from the ECU male connector. It consistently showed 820-830 ohms, which is will inside the spec.

I reconnected ECU and started. W/ engine cold idle went to 1500 and no CEL. After a minute or so, the idle slowed and slight roughness followed by CEL. I tried holding the idle at 1500 rpm and ran for some time, but eventually I got random miss followed by CEL again.

My gut tells me the distributor is the problem, but everything points to ECU. I've located some used replacements and will try to purchase. Price ranges from $45-$70.

thanks

 

An update.

I decided to examine the signal generated by the CYP sensor to see if that would provide any hint of a problem.

I first backprobed the TDC sensor at the distributor connector (identical to CYP) to see what type of signal was being generated. I used an old oscilloscope that I've had for almost 40 yrs (still works!) to examine signal amplitude and frequency. Frequency appeared to be in the low frequency range (< 10hz) I expected. Frequency= RPM/2/60 =~7 hz. Amplitude appeared to be 2-3 volts and was a very abrupt vertical spike as measured.

I next examined the suspect CYP sensor and got essentially same signal.

So, I've purchased a used ECM (95 EX 37820-POA-A51) from local salvage yard, $45+tax.

I'll update again when I hopefully will find the ECM was indeed the problem.

One other possibility has occurred to me. The wiring diagrams all show an external shield on the CYP, TDC, CKP sensors however I've been unable to locate any shielding. This might allow "cross-talk" leading to faulty sensor errors. This seems unlikely since the vehicle ran fine for years in the same condition. But I was curious if anyone has seen any electrical shields on the distributor wiring?

Regards

 

The wires coming out of the distributor might already be coax/shielded. But speaking of shielding, does your distributor still have that plastic-looking shield between the rotor and the CYP/CKP/TDC sensors?

The different timing sensors would have different frequencies, for example 1x, 2x, or 4x per revolution of the camshaft.

 

Well, I installed the used 95 ECM this afternoon and was surprised to fix the problem! I had resigned myself that I was probably wasting $45 on a ECM when I already had a good unit. However it started and ran like a top w/ no Code 9.

I re-examined the removed ECM circuit board, and again found no gross signs of damage. I examined the CYP, and other sensor pins where they bridge from connector to circuit board. There was some indication of possible solder fatigue failure around the pins, and that may be the problem. However, I decided to simply store the part in case I were to have same problem w/ present working unit.

There is only one pickup per sensor (CYP, CKP, and TDC) in the distributor.

None of the sensor wires have shielding that I've inspected. Not sure why all diagrams depict shielding.

Regards

 

Hi,

I also have the same issue on my 1994 honda accord dx.

A year ago, valve cover gasket leaked. Apparently messed up my distributor, ECU affected, one way or another, fuel pump.

Reason i mention this, is because I have changed all these (ECU, Valve cover gasket, Distributor, Fuel Pump.

Half a month ago, valve cover gasket had to be changed again(initially changed by a local, unlicensed mech). This time was done by a Shop that specializes on Hondas. After that, started coming up with CEL. ANd when that initially lights up, sounds like it's running out of gas. However, if i rev it a bit, it continues to run without issues, but CEL stays on.

I checked the ECU using the paperclip method and came up consistently with DTC code 9. Then it went away for the whole week last week. This morning, halfway to my 38 mile travel, started acting up again, same issue, sounded like it was gonna fail, and the CEL lit up again. Stopped at a gas station, left it running, engine sounded normal after a minute or so, and was able to go all the way to work with the CEL on, but running fine.

Someone from another forum (2carpros.com) said Distributor is failing. I have no issues replacing the distributor, but i wanted a second opinion before i did that.

Any help or input would be greatly appreciated.