No Crank No Start Dodge Van

Cougar · August 6, 2018, 5:05pm

I already explained how to verify the circuit operation at pin 85 of the relay in a previous post. From what you stated earlier about the voltage going to near zero volts at the PCM AND ALSO at PIN 85 indicates that the circuit is working correctly, if what you say is true.

Cougar:

Like Tester and Nevada_545 stated, pin C1-8 controls the Engine Start Relay by making a GROUND connection to the relay coil when the key is in the START position so you should see the voltage go to near zero volts when the circuit is ON. Earlier you stated that you checked that wire and it had good continuity. If all that is true then you should see the same voltage change at the relay on pin 85 and the relay should close. The voltage on the pin should drop to near zero volts, which is ground potential. When you are not in the START position then the PCM circuit OPENS and the voltage goes high due to the high resistance added to the circuit. That voltage comes through the relay coil and then meets the very high resistance of the open circuit inside the PCM control circuit because it is OFF, thus no current flow through the circuit. When the circuit turns ON that internal resistance inside the PCM goes to near zero ohms or ground potential and you now have no voltage potential at that point because all the voltage gets dropped across the relay coil due to the current flow through the relay coil, there is now no added resistance for a voltage drop to take place. If you don’t see that same voltage drop on pin 85 of the relay when in the START mode then that wire connection has a problem.

George_San_Jose1 · August 7, 2018, 1:24am

If you measure battery voltage between pin 86 and 85 with the key in start, that part is working. If you can see that relay (in the pdc), you may also be able to hear or feel it click.