Intermittent no start and need clarification on crankshaft position sensor

DOUGH123

MEMBER
1995 HONDA ACCORD
2.2L
4 CYL
MANUAL
260,000 MILES

We have been troubleshooting an intermittent no start condition on our car and have determined that the issue is we have no injector pulse (we have injector power as well as spark plug spark). We are at the stage where we would like to check the crankcase position sensor, but this is where we need some clarification on this year/make vehicle. When we look up this part (or if we have an auto parts store look it up) we get the part shown in the attached picture who's location should be the same as in the picture of the 1997 Accord (attached). When we get under the car and look for the wiring harness that should be coming from the crank case cover, we see none. If we consult the Haynes manual and the wiring diagrams it says "Not possible to include all wiring diagrams for all years. These are the typical and most common." and then shows that this model "should" have three sensors (CKP, TDC, and CYP) in the distributor (and does not address the crankshaft). An inspection of the distributor shows that these three sensors are present, and they each ohm out at 800 ohms, which is in the acceptable range. My questions are: 1) Since I have the three sensors in the distributor, does that mean that there is no additional crankshaft sensor in this car, like in the attached pictures? 2) If it turns out that this car does have the additional crankshaft sensor, how can we locate the wiring harness to test it without having to pull the front cover? 3) Once we test the sensors in the distributor for proper output (and crankshaft sensor if it exists), if they are good where would you suggest we look next?

Thanks,
Doug

8 Replies

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi Doug and welcome to 2CarPros.

The crankshaft position sensor is located in the distributor and there is no additional sensor. The CKP sensor determines timing for Fuel Injection and ignition of each cylinder and also detects Engine speed. The TDC sensor determines Ignition Timing at start-up (cranking) and when crank angle is abnormal. The CYP Sensor detects the position of number one cylinder for sequential fuel injection to each cylinder. With that in mind, my first suspect would be a poor connection a bad connection, a weak crank pick up coil, or even dirt.

I attached a picture of the components in the distributor. Let me know if this helps. If you are looking for specific wiring diagrams, let me know. However, there isn't a schematic for a traditional crankshaft position sensor.

Let me know what I can do to help.

Take care,
Joe

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Monday, January 21st, 2019 AT 5:10 PM

DOUGH123

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Hi Joe,

Thanks for the info, it was helpful. The car mysteriously started working again (which has been they way it goes with this problem) but we were able to get some test done and will be ready to perform them again when the car acts up again. I did measure the CKP, CYP and TDC sensors while cranking the car over (but not actually running it) by measuring with the distributor connector unplugged, tomorrow I will back probe it and get some readings with the car running. Here is what I'm being told are the desired readings and what I measured:

desired measured
Sensor (@800 rpm) (while cranking over)

CKP 2.5 - 3vac 1.6 vac
CYP 0.7 vac 0.17 vac
TDC 2.0 vac 0.5 vac

Since my readings are taking only while cranking over, I'm not sure if I can really draw any conclusions yet. When I back probe it I'll send you the new readings.

Thanks,
Doug

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Tuesday, January 22nd, 2019 AT 7:49 PM

DOUGH123

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5 POSTS

I guess the formatting got removed. Here is that info again:

Desired readings at 800 rpm:
CKP: 2.5 - 3.0 vac
CYP: 0.7 vac
TDC: 2.0 vac

Measured readings taken while cranking over (dist connector unplugged):
CKP: 1.6 vac
CYP: 0.17 vac
TDC: 0.5 vac

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Tuesday, January 22nd, 2019 AT 7:54 PM

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Doug:

You indicated that it cranks at 800 RPM. Are you sure that's correct? That doesn't sound right.

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Wednesday, January 23rd, 2019 AT 4:39 PM

DOUGH123

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5 POSTS

Hi Joe,

I don't think I expressed that last message properly. What I meant was that my readings were taken while only cranking the car over, not starting it. And that the readings I found online were for an engine running at 800 rpm (at idle). And as such I didn't think my readings would tell us much until I could take them at idle speed.

Today I back probed the distributor and got readings at about 850 rpm. I also measured the frequency. Here are the readings:

RPM 850
CKP: Voltage = 4.70 VAC; Freq = 160Hz
TDC: Voltage = 1.70 VAC; Freq = 29 Hz
CYP: Voltage = 0.47 VAC; Freq = 58 Hz

It looks like my TDC is a bit low and my CYP is a little more than half of what it should be. How do these numbers look to you?

Thanks,
Doug

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Wednesday, January 23rd, 2019 AT 8:43 PM

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi Doug.

I was wondering how it was cranking @ 800rpms not running. LOL That would be one heck of a starter.

Anyway, based on what you indicated, my first suspect is the CYP. The TDC isn't off to a degree that I feel it would cause the problem. However, anything is possible. I would start with the cylinder position sensor.

Let me know if that takes care of it.

Joe

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Thursday, January 24th, 2019 AT 4:49 PM

DOUGH123

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5 POSTS

Hi Joe,

I wanted to give you an update and get your perspective again: My buddy has not bought the CYP sensor yet, as he is considering getting the whole distributor, as they are close in price. While waiting for him to make up his mind he said something about his intermittent "no start" problem that made me think that he might have more than just a problem with his CYP sensor. He said: "Normally when I turn the ignition to ON, the check engine light comes on for a moment and then goes off, and if I crank the engine over it will start. But I can always tell when the car isn't going to start because the check engine light will come on and stay ON the entire time, and then cranking the engine will not start the car". And if you recall we were able to determine by troubleshooting that when his car has this "no start" problem it is due to lack of injector pulse.

This leads me to what I wanted to run by you.

The CYP, TDC, and CKP sensors only generate a voltage when the distributor is turning, otherwise they do nothing, correct. So how is it that when his Honda is going to have the no start problem, that the check engine light comes on and stays on prior to cranking the car over? If it was because the ECM was looking for continuity on the sensors prior to start, then unplugging the connector from the distributor should also generate this same check engine light error, but it does not. Unplugging the distributor cable does not cause the check engine light to come on. Would you say this points to a potential problem in the ECM? As for the check engine light, he claims he cannot get a code out for this error because it is OBD1 and he is using an adapter, though I'm not sure how correct that statement really is.

Please let me know what you think of this as I'm hesitant to have him spend money on the distributor or the sensors just.

Thanks
Doug

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Monday, February 18th, 2019 AT 7:39 PM

JACOBANDNICKOLAS

MECHANIC
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Doug, welcome back:

Take a live data scanner and when this happens, check to see if there is a crank signal/RPM signal. Also, when the light stays on, see if you can connect with the computer and if it indicates any trouble codes. I agree with what you are saying. There is no signal until the engine cranks. Start simple by checking grounds.

Let me know.
Joe

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Monday, February 18th, 2019 AT 8:00 PM