Extending crank position sensor cable

[bmwandhonda]

I am going to extend my crank position sensor cable (to re-run in a more concealed method) and am a bit worried it may effect how the ecu will read the signal. Although from what I understand the signal is sent as a pulsating on/off signal (I think) rather than a resistance based signal. Or am I way off?

[jlevie]

The CPS cable is shielded and that shielding must be preserved. If it is run through the plastic wiring case on the front of the timing cover it isn't all that visible. So I f\don't see why you'd bother.

[FLG]

Agreed, its actually sends A/C voltage to the DME.

My fan pulley chopped up the sensor and left me stranded, ripped out some non oem speaker wire the PO put in and spliced it in....worked fine for a week but i wouldnt leave a non sheilded cable like that.

Also i noticed some OEM CPS cables are longer then others?

[SpecM]

Actually the cps sends a DC signal. My cps signal is getting fuzzy at the dme so I need to run a fresh cable anyway. I was going to run it around the side of the water pump, up the head and tuck it next to the fuel rail above the head. That way it will avoid the pulley and any EMI from the alternator wire. I am using a sheilded twisted pair signal cable. Most any electronic supply store has it in bulk. But remember, you must ground the shielding so as to properly disperse EMI

Sent from my Vortex using Tapatalk 2

[FLG]

CPS sends an A/C signal not D/C

My plastic bracket is long gone, run mine up along the side of the cylinder head.

[jlevie]

Agreed, its actually sends A/C voltage to the DME.

My fan pulley chopped up the sensor and left me stranded, ripped out some non oem speaker wire the PO put in and spliced it in....worked fine for a week but i wouldnt leave a non sheilded cable like that.

The only way that is going to happen is if the wiring chase is missing, broken, or the cable wasn't routed in the chase. So the long term fix is to install the cable the right way.

[FLG]

Yep, mine was missing. I agree extending the cable isnt a good solution. I just route mine along the side of the cylinder head behind the little hoist bracket.

[jlevie]

Actually the cps sends a DC signal. My cps signal is getting fuzzy at the dme so I need to run a fresh cable anyway. I was going to run it around the side of the water pump, up the head and tuck it next to the fuel rail above the head. That way it will avoid the pulley and any EMI from the alternator wire. I am using a sheilded twisted pair signal cable. Most any electronic supply store has it in bulk. But remember, you must ground the shielding so as to properly disperse EMI

Shielded twisted pair is the wrong type of fire for this application. The right wire is a pair of individually shielded miniature coax. The ground for the shield is only at the DME end.

Running the wire in the standard location is about as good as it gets w/respect to RFI. If the signal is fuzzy at the DME, the CPS is bad, or the engine harness is bad. I have three used harnesses that have bad wires for the CPS signal and one that has an internal short between the gage and ECT sensor and +12v. Age, vibration, and heat kills the wiring in the harness. If you have a 20'ish year old harness that doesn't have problems, consider yourself lucky but don't be surprised if problems occur.

[bmwandhonda]

Hey thanks for the quick responses guys :) I know what you mean in regards to the stock method being the best method in this aspect. And I was referring to the loom end that would run across the firewall. The actual sensor and wire is fine (at least I think it is) but I was actually re-running the cable from the DME inside the cabin behind the dash and through the firewall next to where the fuse box would usually sit. So was going to extend the centre part of it (befor the connector which would sit on the diagnostics port bracket) I have found some very similar shielded cable which would do the job, the main question is that would the extra length effect the signal (in a bad way) going to the DME (assuming the joins were decent and the shield was also joined)?

Or should I just do a join where I have already cut it, keep the length as is and just have the one or two small cables still running along the firewall. I am thinking at this stage the second option would be the smarter one.

[bmwandhonda]

This is the inner cores of the CPS and I can't see how a decent join of the two cores and the shield will make too much of a difference (admittedly being not as good as an intact factory cable) and then sufficient shielding be placed over the join to stop any interference from other cables. But I am no expert control wiring pro so I am just making assumptions (I am an electrician so I have some knowledge of cables etc just not on this small scale and not much with control type wiring)

Thanks again for your input on this guys :)

[Gregs///M]

Just to confirm the signal is indeed an AC signal. Alternating current.

Foil shielded twisted pair 22AWG - 18AWG recommended. Instrumentation cable should be used. The wire conductor size from a shielded network cable is a bit thin.

Alternatively, a pair of coaxial cable can be used successfully.

[jelias17]

Help Please!!!

Hey guys sorry to bring back an old thread but I desperately need your help, I decided to cut and splice together the wires for the CPS and the tach sensor and now the car only runs on 2 cylinders. I have no problem replacing the sensors but I don’t know how I’m going to replace the harness wiring that plug into the sensors. What do I need to do? Any help is greatly appreciated. It’s is an 86 325e by the way

[jeffnhiscars]

Those sensors are $40@ brand new and they are both the same. EZPZ

[jrobie79]

for the m42, I know the e36 CPS i bought was longer than the stock one. I have an e36 m42 so that's why I bought that one. Not sure how it is on other engines