1997 Chevrolet Suburban, Cruise Control Inop

This 1997 Chevrolet Suburban came in with the complaint that the cruise would work sometimes. This repair applies to multiple Chevrolet and GMC trucks and vans that use the cruise servo number 25315088, gasoline only, no diesels. For a list of these vehicles please go to the ACDelco website and you will find a tab labeled “Vehicle List”. Enter the part number there it will open up a list of vehicles that this part and repair apply to.

The cruise control servo is located under the hood on the driver’s side of the vehicle. It is between the master cylinder and the driver’s inner fender panel. You will need a voltmeter for this test. Preferably one that will read frequency or hertz. After disconnecting the harness connector you should notice that there are letters on the side of the connector body as shown below.

I use a test lead with the correct size terminal on the end. If you use just the meter test lead, use a very gentle touch. If you press too hard you will distort the terminals and render the connector useless. The picture below shows the meter connected and a nominal battery voltage reading.

  • A Cruise On/Off Switch,Grey, 12 Volts
  • B Set/Coast Switch, Dk Blue, 12 Volts
  • C Resume/Accel Switch, Gry/Blk, 12 Volts
  • D Brake /Clutch Pedal, Purple Or Brn/Wht, 12 Volts Key On, O Volts Pedal Depressed
  • E Ground, Blk/Wht, 12 Volts Checked to Battery Positive
  • F Cruise Fuse #6, Brown, 12 Volts Key On
  • G Brake Applied Input,White, 12 Volts Pedal Depressed
  • H Blank/Sealed
  • J Cruise Status, Lt Blue, 12 Volts from VCM/Computer, .125-.350 Volts With Cruise Engaged, The Cruise Module Pulls The 12 Volt Signal Low
  • K Vehicle Speed Input, Dk Grn/Wht, O, 4.5 or 9 Volts as Rear Wheels Turn With Key Voltage Fluctuates

All of the test signals on this vehicle were good. Diagnosis of faulty cruise servo. There are three screws that hold the servo in place. Two on the right side if the picture and one on the left behind the electrical harness connector, where testing was done.

Once the module/servo is unbolted the the retaining tabs for the throttle cable can be depressed and then the cable can be pulled out with a rocking motion. It can be a little difficult as there is an o-ring that may have to be persuaded to come loose.

Once the main cable is pulled loose from the module/servo there is basically a ball and hook that have to be disconnected.

Note here that the end of the cable connected to the throttle linkage has to be disconnected in order to remove the ball from the hook.

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