I've been having some CPS issues, and I think my problem could actually be with my PCM. I know the PCM generates a control voltage, that gets sent to the CPS. The CPS then sends it's generated signal back to the PCM for fuel delivery and timing. Here's what I'm looking for.
Does anybody know what the refrence voltage value is that the PCM sends to the CPS? Is it a 5V signal?
Thanks for the :bump:. So nobody knows? I think it's a 5V signal, just having a tough time pinning it down. Going to check voltage coming down the lines today. Also going to test voltage drop, and resistance of the sensor.
Robsr, Excellent. Thanks. Do you by chance know what the resistance should be on the CPS? Not that big of a deal, just wondering. (since it's an easy measurement to get)
Also there is a battery voltage wire 12.4 voltson the dark green one (I think) or so and the other is a ground
The odd thing is that the battery voltage wire has NO amprage so it will not light a test light. Don't think there is resistance in the cmp it just detects the magnetic signal.
The CPS is a magnetic hall effect sensor. It's fed a ref. voltage, and the teeth on the tone ring on the cam shaft, make it act just like a wheel speed sensor. When a tooth is in front of the sensor, it allows the ref. voltage to pass back to the PCM. When there is not a tooth in front of the sensor, then the voltage is not allowed to pass back to the PCM. Think of it like a solid state light switch. The wires will be a voltage in, voltage out, and ground.
Ok. Fineally had some time to troubleshoot today. I checked the voltage that the CPS is supposed to be receiving. (5v ref., +/- .5v) Hahahahahaha, my poor CPS's have been sucking up a full 12.6v. No wonder why they've been burning out so quickly.
So, a new PCM it is. I really wish I could get a schematic of the inside workings of the PCM. If I could figure out what's used to knock the 12v's down to 5v, I'm sure it would be a lot cheaper to replace that, than the whole PCM at $512. (besides, whoever gets the core PCM, is just going to remanufacture it, and replace the defective part, then sell it for another $512. I'm beginning to think I'm in the wrong line of work :tard
NO NO Hell no dont do that!!! there is a battery voltage reference wire that will read batt voltage... is that what you are seeing? There is another wire/pin that will read 5.4 or something close this is the voltage from the pcm.
Ok. The CPS is a Hall Effect sensor. It's a 3 wire sensor. The wires are:
1. Refrence Voltage (from PCM to CPS)- 5v
2. Signal wire (from CPS to PCM)
3. Ground wire
Ford uses a 5v refrence. To my knowledge, the only manufacturer that uses full battery voltage for their refrence voltage is Hundai.
So, here's the thing. On a wire that I'm supposed to be seeing 4.5-5v on, I'm seeing full battery voltage.
So, with all that being said, if I'm seeing full battery voltage on wire, that I"m supposed to only see 4.5-5v on, and the problem isn't with the voltage regulator within PCM, then what do you suspect the culprit is?
I found a PCM for $100, so that's pretty tempting to try. Heck of a lot better than $500+
On my truck I had cmp issues also. I have them resolved now. But my wires still read 0 voltage (the ground) 5.4 (pcm to cmp) and 12.4 (cmp to pcm) the 12.4 voltage wire has no ampres on it and will not light a test light. I don't know why it is there but mine runs with it. My issue was in the plug. It would lose contact for a millisecond and throw a check engine light, defuel and eventually quit. I replaced the plug and that solved the problem. But that voltage is still there. Have you put one of the old burned out cmp's back in it. They might not be as burned out as you think. I would try messing with the wire while it is running. That is how I finally found mine.
I doubt you have full battery voltage on your signal wire, otherwise you should be burning up your PCM. Plus, 12.4 V would very easily light a test light. (as a test light is a low impedance piece of test equipment) You should have the same 5V refrence voltage on your signal wire that you do on your refrence wire. (the CPS just acts like a switch, producing a digital, "on/ off" transmission for the PCM to interpret)
My truck does not defuel. It runs as though all 4 tires are flat, with massive shuddering thoughout the vehicle. This continues, with power dropping drastically, until I'm running on 1 or 2 cylinders. (it's a timing issue, as the PCM doesn't know when to tell the injectors to fire)
I have tried using old CPS's, and they don't make any difference. The only thing that makes the symptoms go away, is a NEW CPS. Then, about 200 miles later, it's a repeat.
In regards to your replacement of the CPS plug. Did you order the plug from Ford, or did you go through an aftermarket comany like Autozone or Napa? I'm sure the cost of a plug/ pigtail is tons less than that of a PCM, new or used, so it's therefore worth a shot. (at 252Kmi, it's probably about due for a new plug anyways)
mike
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