Crank Position Sensor connector question

potshotscott

Registered User
Hey all, quick question here. I have a 94 SC that has an intermittent no start problem. I pulled my CPS this week and swapped it out for another I had. The resistance on both sensors were the same. The connector harness however does not give me that "feel good click" when I place it on the Crank Sensor. I have to imagine this is abnormal but wanted a second or third opinion on this. Thoughts?
 
The click is when the external plastic keeper grabs. If you want to worry about something, worry about if the metal pins & tangs are making reliable contact inside the connector. Even if the keeper gave a satisfying snap when seated, that feedback doesn't mean there is good contact between the metal bits that do all the work.

If the keeper is broken, de-pin the plastic connector and replace it.

If you can't decide if the metal bits are reliably mating, or it feels like something is jammed and not allowing the connector to seat (some connectors have a rubber gasket inside, and sometimes they get doubled up by mistake...take a head count), and you don't feel like backprobing & checking voltage drop & resistance, on the car, de-pin and do a visual check.

It's possible to gently bend the female tangs a bit to insure they hold, but if they are corroded or otherwise abused, it's time to replace. That can mean replacing a harness, or if on the sensor side, replacing the sensor (as opposed to splicing another connector...dealer's choice).
 
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Thanks for the suggestion. I will take a look. I'm pretty certain there are some mid 90's Mustang 3.8s in the u-pull near me. I'm planning a run to snag a wire harness, connector and sensor off a vehicle to have everything covered. I'm really at a loss at this point. The car will start most of the time but it idles at 2000 RPM. Very odd indeed. Not quite sure what's going on but I'm about to do some searching here on the forums and in my factory books.
 
Huge thank you to the forum owner and all who help

So I just have to say - thank you - for all the information that is stored here. I also appreciate people like KMT and Sam Jones who are consistently polite and very knowledgeable. I read the thread here -> http://www.sccoa.com/forums/showthread.php?103851-Extreme-high-idle/page2&highlight=high+idle <- and learned a LOT.

I recently replaced the ECT in my SC for cooling fan not coming on (and it popped a code too). For some reason I trusted the new Motorcraft part that I put in - bad choice. The ECT I had installed was causing the high idle conditions. Pulled the ECT plug this morning and the car started right up.

It's not clear to me who maintains this forum but I am very grateful its here. THANK YOU.

KMT ECT Quote.JPG
 
Update - now with more frustration! ;)

So here's a good one. I'm pulling KOEO codes and I've seen the following over the weekend.

10 #1 cylinder balance?
118 ECT
121 TPS
113 IAT
335 EGR

About to throw down on a new PCM as I'm having trouble trusting the current unit. Sometimes the car starts right up and operates normally - other times its utter garbage and refuses to start. Am going to check all grounds (have the EVTM) tonight.

I've got about 30K Ohms on my new ECT. According to what I've read here it should be good. Anyone have any additional thoughts?
 
A '10' is a pause/separator, not a code.

If the engine was completely warmed up and goose tested at the appropriate time etc., those are confusing codes to all see at the same time... I'd wonder more about harness and grounds than combined component fails.

Do you know if the ECU is even the right one?

I've got about 30K Ohms on my new ECT.

I no longer test ohms when looking at the ECT. I test volts now days.

Which of These is Not a Symptom of a Potentially Bad ECT Sensor?

  • Continuous rich air-fuel mixture
  • Continuous lean air-fuel mixture
  • Rough idle
  • Engine misfire
  • Engine stalling
  • Increased emissions
  • Increased fuel consumption
Answer is: misfire…


LG/Y is signal out at ECT. This goes to EEC. Backprobe it to check when engine runs and heats up. Ground black lead off DVOM to complete circuit to test. If meter does not auto range, be sure to use lower scale to read DC 5v and less.

Spec for low speed fan turn on is 0.37v coming out of the ECT, at it's connector. Must be above 50° ambient.

This is what I observed on my '90 Anny SC (cooling system stock except for aluminum radiator, only things not replaced over time are heater core & heat exchanger at the oil filter):
• 0.60v = 194°, below N on the gauge, stock thermostat 195°
• 0.53v = 200°~ 205° and N on the gauge
• 0.46 left side of O, 212~215°
• 0.42 almost straight up O ~ R, 218°?
• 0.39 220°~222° low speed fan turn on, left side of R
• Fan comes on and drives it back to N +/- depending on load and ambient air temp, etc.

References...
Temperature|Resistance (K Ω)|Voltage Drop
  • 50° F (10° C) 58.75 Ω 3.51 V DC
  • 68° F (20° C) 37.30 Ω 3.07 V DC
  • 86° F (30° C) 24.27 Ω 2.60 V DC
  • 104° F (40° C) 16.15 Ω 2.13 V DC
  • 122° F (50° C) 10.97 Ω 1.7 V DC
  • 140° F (60° C) 7.70 Ω 1.33 V DC
  • 158° F (70° C) 5.37 Ω 1.02 V DC
  • 176° F (80° C) 3.84 Ω 0.78 V DC
  • 194° F (90° C) 2.80 Ω 0.60 V DC
  • 212° F (100° C) 2.07 Ω 0.46 V DC
 
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Outstanding info once again. The main problem is I'm still getting the intermittent start. I plucked a good quality CPS connector and plan to replace the connector in my car along with putting the old crank sensor in. Once I can get it to start reliably I'll be able to warm it up and pull codes.
 
Good afternoon



For the intermittent start have you checked fuel pressure? Is fuel pressure within limits with Key On Engine Off in timed increments? Example 5 - 15 - 25 minutes.

What is the condition of the IRCM?

Cycle Key On Engine Off and few times and have someone listen for for relay clicks at the IRCM. 1994 - 1995 IRCM have both the EEC and Fuel pump relays. If delayed (> 2 seconds) and or no clicks gain access to the IRCM and lightly tap the box (example a 12 x 3/8 " extension). If click(s) can now be heard attempt to start engine. If engine starts shut down and do the following:

Inspect IRCM connector pins for voltage (requires EVTM), corrosion and or damage. If no defects are found replace IRCM for intermittent relay operation.


Check the MAF. Clean elements/probes. Remove MAF from housing and check the O-ring for security. Check voltage. See post below.

http://www.sccoa.com/forums/showthr...placed-MAF-now-pig-rich&p=1121420#post1121420
 
Thread update: The ECU is the correct one. I finally got a GOOD ECT sensor and burped the car after I got it started. Idle calmed down and now the temp gauge sits in the middle while my ECT sits at 0.63 VDC. Seems as though the car runs exactly as it ought to.

I had 10.5 V at the fuel cutoff safety switch in the trunk so the IRCM has to be good (at least for tonight). I will be watching that going forward and will not likely take the car out of cell range or more than 20 miles until I can "trust" it.
 
Welp - my IRCM is not working correctly in terms of the fuel pump circuit. I have 12V going in but I don't have 12V coming out to head to the fuel pump shutoff switch in the trunk. The car has spark and cranks but won't start tonight. I have my IRCM apart and am working to source the relay I'd need (G8H-UA-007108). I need to go back and see if I'm getting my ground signal on pin 18 at the IRCM coming from pin 22 on the PCM.

I'll either be looking for an IRCM or a PCM....
 
Can one of you tell me what I should read on Pin 18 at the IRCM connector? It looks like it ought to be some sort of ground since pin 13 has Voltage applied from the EEC-IV power relay. I have to assume that the PCM provides a ground to throw the relay. I've removed my relay and it does work but it does not work in the circuit. I am starting to suspect I have a bad PCM as I have to imagine that pin 18 on the IRCM (pin 22 on PCM) has to be a ground when the key is in the on position.

Any of you 1994/1995 SC owners care to confirm?
 
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