GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Chevy K Silverado - 4WD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - Allison 🢒 DTC P1860

Circuit Description

The torque converter clutch (TCC) solenoid, F solenoid, is a pulse width modulated (PWM) solenoid. Pulse width modulation occurs when the signal from the transmission control module (TCM), to a solenoid, is modulated at an established frequency, causing the steel check ball in the solenoid to rapidly open and close the solenoid passage. This serves to vary the output fluid pressure.

DTC P1860 is a type B DTC.

Conditions for Running the DTC
    • The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
    • Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
    • The TCC is commanded ON.

Conditions for Setting the DTC

DTC P1860 sets when the TCM detects an open circuit, a short to power, or a short to ground in the F solenoid circuit for 1.5 seconds.

Action Taken When the DTC Sets
    • The TCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
    • DTC P1860 will be stored in TCM history.
    • The TCM inhibits TCC engagement.
    • The TCM freezes shift adapts.
    • Reverse operation is disabled.

Conditions for Clearing the DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
    • Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
       - A bent terminal
       - A backed-out terminal
       - A damaged terminal
       - Poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • You may have to drive the vehicle in order to experience a condition.
    • Solenoids are sensitive to battery voltage spikes and poor ground connections.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests the system voltage.

    2.

  2. This step tests the command from the TCM to F solenoid.

    3.

  3. This step tests the wiring harness for opens/shorts.

    4.

  4. This step tests the internal wiring harness.

    5.

  5. This step tests the resistance at F solenoid.

Step

Action

Value

Yes

No

Schematic Reference: Automatic Transmission Controls Schematics

1

Did you perform the Diagnostic System Check - Automatic Transmission?

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Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2
  1. Install the scan tool.
  2. Start the engine.

    3. Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Using the scan tool, measure ignition voltage.

Is the voltage within the specified range?

9-18 V

Go to Step 3

Go to DTC P0562 for low voltage or DTC P0563 for high voltage

3
  1. Turn the ignition OFF.
  2. Disconnect TCM connector C2 (RED).
  3. Install the J 39700 breakout box and the J 43799 breakout box adapter.
  4. Using a DMM, measure voltage between connector C2 terminal 29 and connector C2 terminal 32.
  5. Turn the ignition ON, with the engine OFF.
  6. Use the scan tool, in solenoid test mode, to command F solenoid to ON and OFF.

Is voltage within the specified range?

ON: 10-13 V

OFF: 0.0 V

Go to Step 4

Go to Step 10

4
  1. Turn the ignition OFF.
  2. Disconnect the transmission 20-way connector.
  3. Turn the ignition ON, with the engine OFF.
  4. Using the DMM, measure voltage at the engine side of the transmission 20-way connector terminals J and S.
  5. Use the scan tool, in solenoid test mode, to command F solenoid ON and OFF.

Is voltage within the specified range?

ON: 10-13 V

OFF: 0.0 V

Go to Step 5

Go to Step 7

5
  1. Turn the ignition OFF.
  2. Using a DMM, measure the resistance between terminals J and S of the transmission 20-way connector. Refer to Temperature Versus Resistance .

Is the solenoid resistance within the specified value?

--

Go to Diagnostic Aids

Go to Step 6

6
  1. Remove the oil pan. Refer to Oil Pan Replacement .
  2. Remove the internal wiring harness at F solenoid, TCC connector.
  3. Using a DMM, measure the resistance of F solenoid. Refer to Temperature Versus Resistance .

Is the solenoid resistance within the specified value?

--

Go to Step 8

Go to Step 9

7

Repair the engine wiring harness. Refer to Wiring Harness Replacement .

Did you complete the repair?

--

Go to Step 11

--

8

Replace the automatic transmission (AT) internal wiring harness. Refer to Wiring Harness Replacement .

Did you complete the replacement?

Go to Step 11

--

9

Replace F TCC solenoid. Refer to Control Valve Solenoid Replacement .

Did you complete the replacement?

--

Go to Step 11

--

10

Important: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM.

Replace the TCM. Refer to Transmission Control Module Replacement .

Did you complete the replacement?

--

Go to Step 11

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11

Perform the following procedure in order to verify the repair:

  1. Clear the DTC.
  2. Drive the vehicle under normal operating conditions.
  3. Using the scan tool, monitor TCC slip speed. The TCC must engage/disengage when commanded.
  4. Select Specific DTC.
  5. Enter DTC P1860.

Has the test run and passed?

--

System OK

Go to Step 1