1994 Dodge Intrepid Intrepid (3.5L Auto) wont start. Ran fi

Tiny
XEARO
  • MEMBER
  • 1994 DODGE INTREPID
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 120,000 MILES
According to the shop manual, the PCM wont turn on the following relays ( Fuel Pump, Auto ShutOff ) if a signal is not recieved from the cam and crank position sensors when the key is turned to the on position.
DMM shows no 12V at the relay coils so it seems like either the PCM died, or the crank or camp position sensors.

I am fluent with a DMM and an oscilliscope. I know an oscilliscope can be used to check for the squarewave coming from the sensors. The cam sensor has 3 wires. How can I get a pinout for the sensor - or better yet, how do I test it to find out if its bad? Same with the PCM. Also, anyone ever replaced the crank sensor? It looks really difficult to get to.
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Thursday, October 8th, 2009 AT 3:00 PM

15 Replies

Tiny
JDL
  • EXPERT
Just talking about the fuel pump relay, voltage for switch side of relay, hot all the time--fuse A--20 amp. Voltage to the coil side of relay, fuse 12--10 amp. Goes hot when you turn on the key. The computer controls ground circuit to energize. If your having a voltage problem at the fuel pump relay, check the voltage circuits.

I just wanted to add, at the cam and crank sensor, the orange wire is ref voltage, black with lite blue tracer is ground, for both sensors. The signal wire, crank sensor, gray with black tracer. Cam sensor signal wire, tan with yellow tracer.
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Thursday, October 8th, 2009 AT 3:18 PM
Tiny
XEARO
  • MEMBER
At the cam position sensor, I measured 100mV at the orange wire, and 900mV at the Tan w/yellow wire, and of course 0V at the black ground wire.
When I disconnected the harness from the sensor, I measured exactly the same thing.

I did measurements when the key was switched to th on position and didnt see anything different.

At the crank position sensor, I measured 100mV at the orange wire, 320mV at the Grey w/ black wire and of course 0V at the black ground wire. These were taken at the harness with it unplugged from the crank sensor.

How can I tell if any of these is bad? There is only one scrap yard in town and they dont have an intrepid so if I replace the sensors, I have to pay full price! I dont know if I will be able to get to the crank position sensor to change it so I want to save that as last possibility and try to narrow it down first. If the PCM was causing it not to start would it show codes?

When I turn the key on and off to display codes it doesnt show anything. Do chrysler vehicles show a code at the beggining to show that everything is ok when u do the key thing? I believe for and GM will give an OK code if there are no errors. I didnt get any flashing I dont think.
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Friday, October 9th, 2009 AT 5:55 PM
Tiny
XEARO
  • MEMBER
Straight out of the shop manual: "The automatic shut down (ASD) and fuel pump
relays are mounted externally, but turned on and off
by the powertrain control module through the same
circuit.
The camshaft and crankshaft signals are sent to the
powertrain control module. If the PCM does not receive
both signals within approximately one second of
engine cranking, it deactivates the ASD and fuel
pump relays. When these relays are deactivated,
power is shut off to the fuel injectors, ignition coils,
fuel pump and the heating element in each oxygen
sensor.
14 - 28 FUEL INJECTION" SYSTEM OPERATION"

When I jumped the relay coils (turned them on) I heard the both the realys turn on and I could hear the fuel pump come on, but still no spark. The PCM is obviously not turning this stuff on for a reason. Probably one of those 2 sensors.

Wait! New information.

Nevermind. I bet both sensors are fine. I checked the voltages at the sensors and got 100mV at the two sensors' reference voltage wire. This is supposed to be 8V.
Now this is again straight out of the manual:

"The PCM contains a voltage converter that changes
battery voltage to a regulated 8.0 volts. The 8.0 volts
power the camshaft position sensor, crankshaft position
sensor and vehicle speed sensor. The PCM also
provides a 5.0 volts supply for the engine coolant
temperature sensor, intake air temperature sensor,
manifold absolute pressure sensor and throttle position
sensor."

Bet the "voltage converter" isnt doing its job. Bad PCM. (These PCMs are known to be very cheap and junky). Then again maybe the corrosion in the wires is causing a voltage drop resulting in less than a volt at the sensors. Hmmmmm. Now im finally getting somewhere
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Friday, October 9th, 2009 AT 7:57 PM
Tiny
JDL
  • EXPERT
You can check for correct ref voltage at computer pin, if it is good there and not at the sensor, problem with the wiring circuit? With sensors that share circuits, unplug one sensor when you check the other sensor circuits. Engine cranking, the signal wire is a pulse.
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Saturday, October 10th, 2009 AT 9:34 AM
Tiny
XEARO
  • MEMBER
Good idea. I should measure at the PCM to determine if the wiring is bad or if its the computer.

Is the wire going to be the same color at the PCM? I looked trough the shop manual and I dont see a pin out of the PCM.

By any chance do u know the right pin on the PCM?

Thanks for the help! I think I am close to gettin this old piece of junk running!
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Saturday, October 10th, 2009 AT 7:00 PM
Tiny
JDL
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/170934_intrepid_computer_connector_1.jpg



Pin 7 should be ref voltage. There are numerous sensors that use the same ground. I can't rule out that another sensor might be causing a problem?
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Sunday, October 11th, 2009 AT 9:49 AM
Tiny
XEARO
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You are the man! I will check that pin out later when the temp gets above 40 degrees and see what I find!
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Sunday, October 11th, 2009 AT 11:21 AM
Tiny
XEARO
  • MEMBER
Pin 7 still only shows less than a volt. I even cut the wire so none of the other sensors were drawing current from that ref voltage wire (in case there was a short) and it was the same. So the PCM is not outputting 8V at pin7 so that sounds like the ned of the diagnosis right?

I allready ordered a new PCM. Found one for 10$ plus shipping on ebay. Its form a 95 but it has the same motor and everything.

One question: Some ebay stores say the PCM needs to be reprogrammed to the specific VIN of the vehicle its being put into, but I had at least 2 people tell me that shouldnt be true. Is it?
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Monday, October 12th, 2009 AT 2:55 PM
Tiny
JDL
  • EXPERT
I'm not positive, but, I don't believe the dealer has to reprogram.
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Tuesday, October 13th, 2009 AT 9:39 AM
Tiny
XEARO
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Installed new pcm and everything is exactly identical. Still not outputting 8V. Still the same thing. Measured right at the wire goiin into the computer.

Is there anything that would cause the computer not to output that 8V? Maybe there is some inpute wire that is not correct and it doesnt want to turn on that 8v!

I donloaded a manual but I dont see a complete pinout. Do u have a complete pinout for the computer? I want to check every one (or at least what I think are important) and see if there is something else wrong. Maybe the pcm isnt bad at all and its just not getting power or something.

Do u have a complete pinout for the pcm?
This pcm doesnt want to let me check the codes either. Hmm any ideas? Maybe it really is just another bad pcm. The seller said it was working, and has great ebay feedback.
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Saturday, October 17th, 2009 AT 6:12 PM
Tiny
JDL
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/170934_dodge_intrepid_35_1_1.jpg



http://www.2carpros.com/forum/automotive_pictures/170934_dodge_intrepid35_2_1.jpg



http://www.2carpros.com/forum/automotive_pictures/170934_dodge_intrepid_35_3_1.jpg



Sorry about that, I had to magnify the page in order to make it readable. When I magnify, there is only small part of the page that is visible to copy. I had to copy in three sections. The autozone site has free wiring diagrams, you have to register the vehicle, it's free. With some dodge vehicles there is a dalalink connector under the hood, usually close to battery, it's a hookup for a scanner. I'll double check for your vehicle.
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Sunday, October 18th, 2009 AT 11:46 AM
Tiny
XEARO
  • MEMBER
Hey thanks for the diagram! Autozone provides wiring diagrams? Cool! That will help in the future. I think there is a datalink connector down there but the car is OBD1 (I think? I have scanned for codes in a few obd2 vehicles but in obd1 with a chrystler, you have to turn the key on and off a few times and it will blink the check engine light to signify codes. Well it doesnt, so either it really is obd2 or both computers are fried, or something else =)

i think I saw that datalink connector under there. If I did, I guess I could go borrow a scanner and check it out. The check engine light does not stay on however. So I bet there arre no codes stored.

Well I am going to check a few things based on that pinout. I appreciate it! You have definately been very helpful! I will continue to use this site in the future!

Oh yea. So that datalink connector, I was thinking that was for dodge's special 3000$ scanning tool.
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Sunday, October 18th, 2009 AT 3:13 PM
Tiny
JDL
  • EXPERT
I found this location for the datalink connector. On other makes and models, sometimes the lite won't work, for whatever reason, maybe a scanner will ?


http://www.2carpros.com/forum/automotive_pictures/170934_dodge_intrepid_datalink_connector_1.jpg

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Sunday, October 18th, 2009 AT 4:21 PM
Tiny
XEARO
  • MEMBER
Well I checked voltage going to the pcm and its there, and the grounds all seem to be good (going to the pcm).

So maybe I really did just get another bad pcm.

The 5V and 8V supplys from the pcm are both less than a volt. I assume that means the pcm is bad.

So there is a 6 pin connector under the dash where u were saying, but I dont know if a scanner will work with it. The obd2 connector is much different. And this connector only has 6 pins and is square shaped.

I am going to buy another pcm from a guy 2 towns away and see if that works.
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Tuesday, October 20th, 2009 AT 10:27 AM
Tiny
JDL
  • EXPERT
The scanner I have will work obd1 or global obd11. Takes a different cable adapter for obd 1, depending on the make of vehicle. I have obd1 cable adapter for GM, don't have one for Chrysler. Even in the chrysler family, the connector may be different depending on the model.

I hope it isn't a circuit causing the computer to go bad? It could damage the next one as well?
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Tuesday, October 20th, 2009 AT 10:58 AM

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