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sprinkles08
sprinkles08, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 23006
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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08 2.4l see no rpm signal on scan tool but can measure

Customer Question

08 2.4l see no rpm signal on scan tool but can measure voltage change at crank sensor with dvm. checked for faulty wiring but none found
JA: Does the vehicle stall at low speeds? Does it sputter?
Customer: cranks but will not start, no spark or fuel
JA: What is the model of your '08 Mitsubishi?
Customer: galant
JA: Are you fixing your Galant yourself? What have you tried so far?
Customer: yes, just started to take cover off to see if there are any problems with sensor
JA: Anything else you want the mechanic to know before I connect you?
Customer: the car was parked for 3 months with dead battery, car ran when parked but after battery replacement car will not start
Submitted: 3 months ago.
Category: Mitsubishi
Expert:  sprinkles08 replied 3 months ago.

Hello and welcome to JustAnswer!

Measuing voltage at a sensor just tells you that something is happening inside the sensor but doesn't give an indication of it's actual operation. A labscope is needed to look at the actual signal.

It appears that you have no fuel pressure also, in which case that may point to an engine controller related issue.

Does the ECM communicate with a scan tool?

Customer: replied 3 months ago.
the scan tool communicates, the computer has no codes. when I crank engine the scanner shows 0 rpm. I have disconnected sensor and cranked motor I still have no codes. I'm guessing a bad ecm?
Expert:  sprinkles08 replied 3 months ago.
Is cam signal present?
Customer: replied 3 months ago.
the cam sensor in not listed, the scanner i'm barrowing is older not sure of its updates
Expert:  sprinkles08 replied 3 months ago.
What exactly was done at the sensor?
Customer: replied 3 months ago.
checked wiring it all looks good and measures good(both cam & crank), back probed sensors and turned motor over by hand and watched signal toggle from 0.3 to 5v on dvm(both cam & crank)
Expert:  sprinkles08 replied 3 months ago.
You'll want to also check the crank sensor signal circuit at the ECM and see if it agrees with what you see at the sensor.
Customer: replied 3 months ago.
I will check that next, getting ready for work, I will get back to you with results in the next few days. if that checks out what's the next course of action.
Expert:  sprinkles08 replied 3 months ago.
It would be best to use a labsvope to look at the actual signal but it could be the sensor or the ECM.
Customer: replied 3 months ago.
the crank and cam signals are getting to the ecm. I'm still trying to find a lab scope to check signal shape but no luck yet.
Expert:  sprinkles08 replied 3 months ago.

Ok.

Customer: replied 3 months ago.
I assume the signal should be a square wave
Expert:  sprinkles08 replied 3 months ago.

Yes. If the waveform isn't square then it may not be interpreted.

Customer: replied 3 months ago.
if the engine is cranked with the sensor disconnected shouldn't the computer have a sensor code
Expert:  sprinkles08 replied 3 months ago.

Usually, if the cam sensor is working.

Customer: replied 3 months ago.
if disconnect either sensor and crank the engine I get no fault codes. that's why I thinking the ecm is bad.
Expert:  sprinkles08 replied 3 months ago.

That's definitely possible.

Customer: replied 3 months ago.
I will let you know I find when I get the signals tested
Expert:  sprinkles08 replied 3 months ago.

Sounds great!