Hello all, my girlfriends 97 CL auto with an F22B1 threw check engine P1361 recently and I'm finally making time to address the issue. She has been driving one of my extra cars so time hasn't been and won't be a major constraint. The Car went into limp mode after throwing the CEL, so I pulled the code with a scanner and found that it was the TDC/CKP sensor. I reset the ECU and took it up the block and CEL hit immediately again. My background is with older (OBD0/OBD1 B series) engines so I searched around and referenced my copy of the FSM for her car. The labor is not an issue, I have that handled.

My question is, how do the TDC/CKP sensors work? How does it gather its information? From my research it reads off the nubs on the balancer belt drive pulley, correct? Only thing I'm not fully understanding is how? The reason I ask is that I waited to order the replacement sensor until I tore it down and could see if anything was amiss once I got it apart. From the reading I've done it isn't extremely common that they fail on this model and the lack of urgency to get it back on the road led me to wait after seeing the price for a new unit from the dealership.

So anyway, I got it apart and found that the surface of the sensor was extremely dirty. The face of the sensor is covered with grease. It's obviously being slung onto it with the belts rotation so I'll definitely have to track down where it's coming from and correct it while it's apart. From the pictures I'm posting though, could this cause the sensor to misread? I don't know enough about how it works to know if it could affect it or if the grime is unrelated. It isn't so much an issue of "I don't want to buy the part" as much as "I don't want to buy the part if wiping this one off will yield the same results for $250 less." Any input would be appreciated. Thanks!

 

Likely cleaning the sensor while replacing all timing seals will fix your issues.

 

I was thinking along the same lines but without knowing how the sensor gathers information it would be just a guess. As much as I don't want to waste $250 on the part if it's not necessary, I also don't want to clean it and reassemble it only to find that it needs to be done over again because the sensor needed to be replaced.

 

It reads off of the front balance shaft pulley. Obviously if the sensor is dirty and cant read it wont be able to function.

 

They are Variable Reluctance sensors, or sometimes referred to as a monopole. They are used to measure position and speed of the engine. These sensor consists of a magnetic pickup, and a rotating toothed wheel. As one of the teeth on the balance shaft gear, or timing belt gear, passes one of the VR sensors the resistance of the sensor changes. This change in resistance is sensed by the ECU and turned into engine RPM(CKP) and engine position (TDC).

Any amount of dirt or metal debris on these sensors may alter the signal to the ECU.

 

Ok, that's the answer I was looking for. Thanks guys!

I'll update this thread after I get it put back together because I couldn't find anything similar while searching.

 

While you had it a part did you check the resistance in the sensors as the P1361 troubleshooting advises?

Here is the Honda shop manual DTC troubleshooting guide for the TDC CKP sensors.

 

I did check resistance of the sensors but that was the extent of the troubleshooting procedures I followed from the FSM. While checking the resistance I was only getting a brief reading from my multimeter before it would go back to open. The brief readings I got were however within spec (1850-2450 according to my FSM). The fact that I couldn't get a steady reading on it led me to believe my sensor was probably faulty although looking back now I probably should have continued on with the troubleshooting procedure before tearing into it. Oh well.

 

You put it back together yet? Being that the sensor uses changes in magnetic fields, that the sensor is mounted so close to the reluctor wheel and that the teeth on the reluctor ring are so tall (roughly 1cm, giving the potential) it doesn't make sense that grease would effect the sensors reading enough to cause a ECU determined fault. Foreign metals could distort the magnetic field of the sensor however.

I would check the resistance readings carefully, GhostAccord's post of the Honda FSM troubleshooting diagram and a multimeter should be all you need to know if you have a bad sensor. You could be like 90% of mechanics and just throw a new sensor in too but thats lame. If it's not the sensor itself it's either the wiring or the ecu itself but I'm betting its gonna need a new sensor...

Also, the ohm (resistance) setting on a multimeter uses the multimeter's battery to send out a current through the two leads, knowing its current output it can determine the resistance between them. This means that a weak multimeter battery can cause incorrect or fluctuating resistance readings. Poor contact on the leads could as well but that one is pretty obvious.

 

No I haven't put it back together yet. I may reinstall the sensors and run through the full troubleshooting flowchart in the FSM and see where it leads me. Right now I'm tempted to run some more diagnostics and if I don't see any blaring failures during any of the tests I'll just clean it and slap it all back together and hope that the contamination was the cause of the misread. It can't hurt, I'm in no rush to get it driving.

 

Just wanted to update this thread in case any future searchers come across a similar problem. I ended up just cleaning the sensors and area under the timing belt covers and put it all back together. Took it for a drive and no more CEL, no more limp mode. I guess the dirt on the sensor was enough to cause it to misread. Thanks to all who responded, I appreciate it!

 

Thanks for the update.

Good to hear that you got it back up and running!