1996 Dodge Ram No cruise P1683 code

This code refers to the speed control servo power circuit open or shorted. The power comes through a normally-on contact in the brake light switch. Use a test light or voltmeter to measure the voltage on the yellow wire / red stripe on the switch. If it's there, measure on the dark blue wire / red stripe. If it's missing there, the switch is defective. The voltage should go to 0 volts there when the pedal is pressed.

Caradiodoc

Sorry about that important detail. The engine must be running, then there must be 12 volts on both wires when the brake pedal is not pressed. It comes into the switch on the yellow wire with red stripe.

The 12 volts leaves the brake light switch and ends up at the servo on the dark blue / red wire.

Caradiodoc

OK, that voltage comes from the Engine Computer, connector 3, pin 11. That's still a yellow / red wire. If it's missing there, check for some voltage on connector 3, pin 32. It's a red wire with light green stripe. The voltage will vary according to which cruise control function switch is pressed. If no voltage appears, suspect a broken clock spring under the steering wheel.

As an alternative, if there is a green "Cruise" light on the dash, the clock spring, on / off switch, and Engine Computer are working if the light turns on. Usually, when the clock spring breaks, it's not long before the horn also doesn't work and the air bag warning light turns on.

Caradiodoc

Hold the phone. The green light is on? Dandy. Things are working up to the Engine Computer. Recheck the voltage at the brake light switch. If you still find 0 volts, double-check the ground for your meter. If you feel confident there's no voltage there, check at the wire in the Engine Computer's connector. If it's missing there, suspect a problem inside the computer. If voltage is there, look for a break in the wire from there to the brake light switch.

Caradiodoc

Check for 12 volts on the same wire at the cruise control servo. If you can't find it, follow its throttle cable from the throttle body. It will lead you to the servo near the battery. The servo will have a four-wire plug. Back-probe the dark blue / red wire. If there's no 12 volts, there's a break in the wire between there and the brake light switch.

If you do find 12 volts, also check on the tan / red wire and the light green / red wire. There should be 12 volts there too. Don't use a test light on them if the engine is running as they could cause the engine to go to wide-open-throttle. Finally, check for voltage on the black wire. If you find any voltage there, the ground wire is open, either in the wire, or more likely, where it is bolted to the body.

The last three wires must be tested while still plugged into the servo, otherwise their voltages are meaningless.

Caradiodoc

Are you referring to the test light at the servo connector or the green "cruise" light on the dash?

If the cruise light goes out, can you turn it back on and off by pressing the button on the steering wheel?

Caradiodoc

Confused. "Not able to turn it back on" but you can shut it off?

If you can not cause the light to change with the switch on the steering wheel, back-probe the red / light green wire in connector # 3 of the Engine Computer, pin 32. The voltage should vary depending on which switch is pressed. Typically, if a wire is broken, there will be 0 volts there regardless of which switch is pressed. If you find some voltage when the "Resume" or "Cancel" buttons are pressed, the wires are good. If you find pressing the "On" button results in the same voltage as one of the other buttons, there is a problem with the switches. The computer determines which function was pressed by the voltage that appears on that wire.

Caradiodoc

My manual shows the V32 circuit drawn two different ways on two adjacent pages. It doesn't show the green light, but the voltage has to be coming from the PCM and going to the brake light switch, then to the servo. To double check me, press the brake pedal to open the switch, then there should be voltage on the yellow / red wire. If you find 0 volts, and voltage on the dark blue / red wire, I'm looking at it backwards.

Also, if I'm wrong, there will be no voltage on either wire if the servo is unplugged.

You're right about the yellow / red wire to the switches. I was looking at it as supplying voltages to the PCM, but in fact, the 5.0 comes out of pin 32 of the PCM and is grounded by the switches. Can you monitor the voltage on that wire from under the dash? Does the cruise kick in while the green light is on?

I'm wondering if there's an intermitent break in the clockspring or two circuits are touching at the ends of its ribbon cable. It almost sounds like the PCM is detecting a problem and is shutting the system down in response. That could be due to the detected problem could lead to it going to wide-open-throttle, or the problem could prevent it from getting the cancel signal from the control switch or brake light switch.

Caradiodoc.

If you remove the two tiny screws on the connector cover, you can slide the coils out. There are three coils soldered to the circuit board that the connector pins are soldered to. Had one warranty unit the had a broken wire right on the end of the coil of wire where it was soldered to the terminal. Resoldered it and had a good working servo.

There's tiny rubber pads that open vacuum passages. They are controlled by the coils.

Do you see a change in voltage on the red / light green wire from the steering wheel switches while driving?

Caradiodoc