P1870

DTC P1870 Transmission Component Slipping





Circuit Description

The powertrain control module (PCM) calculates the torque converter clutch (TCC) slip by comparing the engine speed and the transmission output shaft speed. In fourth gear, with the TCC engaged, TCC slip speed should be -20 to +50 RPM. The table above indicates the solenoid and clutch states for the various gear ranges.

If the PCM detects an excessive amount of slip when the TCC should be engaged, then DTC 1870 sets. DTC 1870 is a type B DTC.

Conditions for Running the DTC

- No TP DTCs P0122 or P0123.
- No VSS DTCs P0502 or P0503.
- No TCC enable solenoid electrical DTC P0740.
- No 1-2 solenoid performance DTC P0751.
- No 1-2 solenoid electrical DTC P0753.
- No 2-3 solenoid performance DTC P0756.
- No 2-3 solenoid electrical DTC P0758.
- No TCC PWM solenoid electrical DTC P1860.
- All shift solenoid performance diagnostic counters are zero.
- Not in fuel shut off.
- The throttle angle is 14-35%.
- The transmission is not in first gear.
- The transmission range selector position is D4.
- The transmission fluid temperature is greater than 20°C (68°F).
- The engine torque is 70-230 Nm (50-170 ft lbs).
- The engine speed is 800-5,000 RPM.
- The vehicle speed is 56-132 Km/h (35-82 mph).
- The speed ratio is 0.7-0.995.
- The TCC is commanded ON and at maximum apply for more than 5 seconds.

Conditions for Setting the DTC

DTC P1870 sets if the TCC slip is 200-1,500 RPM for 8 seconds. This must occur 3 times with the TCC commanded OFF between each occurrence.

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

- Ensure the vehicle's final drive ratio matches the PCM calibration.
- Ensure that the transmission will shift through all four gears with the gear select lever in the D4 range.

Test Description

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

NOTE: Step 4 inspects the modulator assembly, which could cause P1870 to set.

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