Circuit Description
The torque converter clutch (TCC) solenoid valve is an ON/OFF (normally OFF) valve which controls the converter clutch apply and release. The torque converter clutch pulse width modulation (TCC PWM) solenoid valve works with the TCC solenoid valve to control the clutch apply rate (feel). The PCM controls the duty cycle on the TCC PWM solenoid valve to regulate the feed pressure to the converter clutch regulator valve, which in turn, regulates the converter clutch apply pressure.
The TCC PWM solenoid valve receives ignition voltage from circuit 1339. The PCM uses throttle position, vehicle speed, and other inputs in order to determine when to energize the solenoid. The PCM controls the ground path on circuit 418 to vary the duty cycle from 0 to 100%. At 0% duty cycle, the converter clutch apply pressure is at maximum. At 100% duty cycle, the converter clutch apply pressure is at minimum.
When the PCM detects a continuous open or short to ground in the TCC PWM solenoid valve circuit, then DTC P1860 sets. DTC P1860 is a type B DTC.
Conditions for Running the DTC
| • | System voltage is 10-18 volts. |
| • | The engine speed is more than 500 RPM for 5 seconds. |
| • | Not in fuel shut off. |
| • | TCC PWM duty cycle is greater than 90%. |
Conditions for Setting the DTC
DTC P1860 sets when the PCM commands duty cycle below 10% or above 90%, and the PCM detects a signal voltage on circuit 418 outside the calibrated limits for 5 seconds.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the conditions exist for setting the DTC. |
| • | The PCM inhibits TCC operation. |
| • | The PCM inhibits 4th gear if the transmission is in the hot mode. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes. |
| • | A scan tool clears the DTC from PCM history. |
| • | The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect the wiring at the PCM, the transmission connector, TCC PWM solenoid connector and all other circuit connecting points for the following conditions: |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Reduced terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| • | When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step isolates the engine harness from the transmission harness.
-
This step verifies that engine harness circuit 418 is not open or shorted to power.
-
This step checks if the solenoid or solenoid circuit is open or shorted.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||||
2 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM. Did either reading pulsate No/Yes/No? | -- | Go to Diagnostic Aids | |||||||||||||
Is the test lamp ON? | -- | |||||||||||||||
4 | Inspect engine harness circuit 418 for an open. Refer to General Electrical Diagnosis in Wiring Systems. Was a condition found? | -- | ||||||||||||||
Important: On the 4T60-E transmission, when the scan tool is used to command the TCC Duty Cycle (PWM Solenoid) ON, the display indicates 99% duty cycle. However, the solenoid will be de-energized (test lamp off). When commanded OFF, the display indicates 0% duty cycle, but the solenoid will be energized (test lamp on). Does the solenoid cycle ON and OFF as commanded? | -- | |||||||||||||||
6 | Inspect engine harness circuit 418 for a short to ground. Refer to General Electrical Diagnosis in Wiring Systems. Was a condition found? | -- | ||||||||||||||
7 | Inspect engine harness circuit 418 for a short to power. Refer to General Electrical Diagnosis in Wiring Systems. Was a condition found? | -- | ||||||||||||||
Is the measured resistance within the specified range? | 10 ohms to 15 ohms | |||||||||||||||
9 | Is the resistance greater than the specified value? | 15 ohms | ||||||||||||||
10 | Inspect transmission harness circuit 839 (RED) and circuit 418 for an open. Refer to General Electrical Diagnosis in Wiring Systems. Was a condition found? | -- | ||||||||||||||
11 | Inspect transmission harness circuit 418 (BLK) for a short to ground or short to power. Refer to General Electrical Diagnosis in Wiring Systems. Was a condition found? | -- | ||||||||||||||
12 | Replace the transmission wiring harness. Refer to Solenoids and Wiring Harness Replacement . Is the replacement complete? | -- | -- | |||||||||||||
13 | Replace the TCC PWM solenoid valve. Refer to Torque Converter Clutch Pulse Width Modulation Solenoid Replacement . Is the replacement complete? | -- | -- | |||||||||||||
14 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Is the replacement complete? | -- | -- | |||||||||||||
15 | Repair the wiring as needed. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||||||
16 | Perform the following in order to verify the repair:
Has the test run and passed? | -- | System OK |
