Two wire CKP sensor question

Hi guys. I'm having difficulty in the setup and interpretation of a CKP sensor waveform on a 1996 Toyota Surf with a 1KZ-TE engine. CKP code is coming in at idle and disappears at around 2000rpm and then comes back again on deceleration. Do I hook up the earth probe and oscilloscope probe accross the sensor? Or do I use common ground and scope either side of the sensor?

Ground to chassis
yellow lead to sensor signal

If you go into guided component tests it will show you how to setup for each sensor. Fyi

This is a variable reluctance sensor, producing an ac-signal. A signal will be present on each of both wires. If you want to measure full amplitude of the signal you have to hook one channel to (any) one of the sensor wires and the ground connection to the other sensor wire. You don't want to use a second channel with this hook up because if you do so you will introduce a ground loop resulting in a "floating" signal on a second, third or fourth channel.

If you want to hook up more than one channel at once than use chassis ground just as Hardtopdr2 recommended.

Thanks guys. I'm trying to make sense of the inconsistent spikes in the signal. Bearin in mind I'm trying to diagnose an engine check light condition that brings a CKP code at idle that disappears at 2000 rpm.

The first two images were taken from either side of the sensor using chassis ground, and these next two were taken full spectrum with the earth on one side of the sensor and the probe on the other side.

Check your voltage setting for ch2 both should be set the same i believe.

Thanks hardtop 2. I wasnt using channel 2. All tests were done on channel 1.

Oh ok lol the first photo in your last post is how it should look.

Thanks again Hardtop. Yes, I agree that the first image is how it's supposed to look, but bear in mind I set a trigger to "zoom" in and freeze it, but I was trying to get a 10sec frame to analyze the consistency of the signal and that where I get those weird spikes. I would have expected to see consistent spikes over a longer time frame? The four progressive spikes which are then immediately inverted has got me stumped.

Another thing that came to me last night at home is I remembered that the rev counter is not working on this vehicle, which leads to to believe that the NE signal on this vehicle may not be working? It's hard to believe because this vehicles starts with no issues and has no drivability issues either, just a CKP code that comes on at idle or deceleration.

Still, I'm not 100% convinced that this is a good CPK signal.

Another thing is the first two images of this thread is either side of the CKP using chassis ground on the oscilloscope. One side is crazy noisy. I would have expected similar patterns?

I noticed in the last two one had a trigger set the last one didn't so that may be why but dunno

Two questions:

Does the vehicle start with the CKP sensor/signal disconnected?

Do you get any rpm reading when you introduce some kind of signal into the CKP harness while disconnected from the sensor?

should he use AC or DC
i think he shold use AC

Ac coupling can be used and with this sensor it may help clean the signal up. Since i had my scanner handy this time i looked up the set up and it should be conected to both wires at sensor connector. Yellow lead to sensor feed and black lead to signal return. The only thing my scope didnt have preset was the ac coupling for this sensor. So i would say as well ch2 should be turned off as that may be causing some of rhe noise on channel 1.

Hi everyone,

I would check:

1. Ignition spikes (primary/secondary) are not causing that noise. Unplug sensor - AC voltage between two wires - check waveform.

2. Toothed wheel is completely clean (no dents/protusions).

3. Replace sensor.

I managed to get a half decent capture of the CKP on channel two and the NE (from the injector pump) on channel one..

To my untrained eye I don't see an issue with this waveform? Why is it bringing on a CKP error code? Any thoughts would be greatly appreciated.

Thanks for the input guafa. This is a 1kz-te Diesel engine from a 1996 Hilux Surf

Oh ok, i see.

Anyway, you should check for any inductive spike from coils. If you unplug sensor and check signal while cranking, you can confirm the source of that noise (toothed wheel or spikes coming from inductive actuators)

Inside pcm, a noise filter (operational amplifier) should select which spikes are real and which are noise, according to their voltage level and it's duty.

The output pin of that filter, is a clean square pulse (usually 5vdc). If you know the output pin of that filter, you can check if those non desirable peaks near the real peak, are causing non desirable pulses that microcontroller is detecting. That must be the cause for the DTC.

Anyway, the root cause are those non desirable peaks.

Ok i have a quick question are you probing the sensor or at the computer/pcm? And if at the sensor where is your sensor located at that your probing? From what i looked up the single wave your getting is the camshaft sensor. Attached is the crank sensor waveform

Ckp is blue
Cmp is red
Injector is green

Thanks hardtop.
I was measuring at the sensors. NE signal is on the injector pump and crank sensor is just in front of the starter.. I'm going to try and get a pin out diagram for the ECU today and test from the ECU. In my limited experience I'm also not happy about the noise I'm picking up. The injectors on this vehicle are mechanical so I'm not sure how. The injector readings on your waveform were captured?