3 Wire CKF sensor Voltage ?

[Rangan]

Hi,
Does anyone know what the voltage should be on the center pin of the 3 pin CKF sensor on a 1998 Honda Civic GX ? There is no voltage there right now as I test it, should it be Sensor voltage ? or Battery 12 V ? That voltage comes from ECU ?
-RD
1998 Honda Civic GX 146K Miles

 

[Rangan]

I had a Crank No Start condition and by process of elimination finally came around to checking the CKF sensor output and there was none. The sensor resistance is within spec ( 2.7 K ) so it had to be wiring, I read that that Pin 2 should have a voltage but there was none. Pins 1 & Pin 3 are not shorted to ground so that is not the problem. The sensor is ok and so is the wiring. for Pin 1 and Pin 3. so the lack on voltage on Pin 2 I thought was causing the ECU to not receive the pulses and hence the No Start condition. Would appreciate if you can tell me how to diagnose this ?

 

[Rangan]

No CKF or other CEL codes, right? If so, look elsewhere.

Start with the basics - Does the fuel pump prime? Bright white spark at all 4 spark plugs? Mechanical timing correct? Good compression in all 4 cylinders?

Yes, Did all that - Strong Spark on all 4 - Good compression on all 4 , This is a CNG so no Fuel pump, but I verified that the CNG gas is at pressure at the fuel rail - Distributor good - Removed , cleaned and tested Fuel Injectors - checks OK. So was down to the last possible cause the CKF - Anything else I can check ?

 

[Rangan]

Doesn't sound like you checked the mechanical timing of the engine. Do that and report back.

If you spray starter fluid into the throttle body, will the engine start?

A bad CKF will make the engine run like crap but generally won't cause a no-start.

Spraying starting fluid did start a few times - but stalls immediately - One thing I also is I did the CKF bypass by shorting C8 with C22 and shorting C9 to 31 after disconnecting the CFK sensor - After that the injectors fire but still no start - Any hints on how to check mechanical timing ?

 

[Rangan]

No CEL codes - The distributor signals all seem to be there as far as I can check according to the manual - The engine runs crappy - jerks around a lot as if it is choking if I continue to spray starting fluid into throttle body.. I inspected the timing belt and it is is good.. Alternator is good as well .. So that left me with this CKF sensor as last resort.. What should be Voltage on C22 ? I can check that both at the ECU as well as at the CKF sensor connector - since C31 is sensor ground and Pin2 is ground..

 

[Rangan]

I have a good OBDII reader - no pending codes also - Just went down and checked the mechanical timing - looks good - I can hear the injectors firing with the CFK bypass, I bench tested the Injectors and they are all good - Since fuel type is CNG I can only assume that gas in present in the engine since I have made sure that CNG is at the fuel rail and injectors are working. The only thing that might not be right is the ECU does not quite like the CFK bypass as the same as the signal from the CFK sensor - and hence it is not firing the injectors - If I can get the CFK sensor working then I can rule that out - and it must be the ECU - although I doubt it would be the ECU.. Any pointers on how to test the CFK voltage and signals ?

 

[Rangan]

The Spark plug wires are stock , I have not changed them, I just replaced the whole distributor a while ago. The ECU I think is original as that has not been replaced..

 

[Rangan]

Yes, I tried that - No CEL codes after re-connecting the CKF sensor and cranking - The Crank No Start condition happened like this - Was driving to work and the Engine cut out suddenly - Since then the car has the Crank No Start condition..

 

[Rangan]

After returning CKF sensor to stock even spraying the starter fluid engine does not run. I will try with CKF bypass over the weekend and update you. The compression numbers I wrote down 2 days ago were as follows 1) 170 , 2) 150 3) 170 4) 170 , all numbers are cylinder numbers 1 through 4..

 

[Rangan]

That I did and there was good spark with and without the CKF bypass..

 

[Rangan]

Yes, will do it over the weekend and also report back on CFK bypass with starter fluid as well.

 

[Rangan]

Yes, I will do that over the weekend and I will also check the starting fluid test with and without CKF bypass.

 

[Rangan]

Finally I got around to doing this after all the rains we had in CA, First sunny weekend in a while - Attached are the TDC marks , looks like they are all lined up, both the top one and the one below. The timing belt looks in great shape , I will change out the CP Sensor since I have the cover off anyway, but I know it is ok as I tested it.. Any pointer as to what I can try next ?

 

[Rangan]

Anyone has any pointers as what else I can check ?

 

[Rangan]

It turned out that it was the Distributor - replace it under warranty as it was less than 6 months old, finally it is humming along.. Thanks to everyone who helped..