P1870

Diagnostic Chart:

Description:

CIRCUIT DESCRIPTION

The Powertrain Control Module (PCM) monitors the difference between engine speed and transmission output speed. In D3 drive range with the Torque Converter Clutch (TCC) engaged, the engine speed should closely match the transmission output speed. In D4 drive range, with the TCC engaged, the TCC slip speed should be -20 to +60 RPM. The table above indicates solenoid states and transmission components that apply during 4th gear with the TCC commanded ON. When the PCM detects excessive TCC slip when the TCC should be engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

CONDITIONS FOR SETTING THE DTC

DTC P1870 sets if the following conditions are met for three TCC cycles with reported excessive TCC slip conditions, two consecutive times.

^ No Throttle Position (TP) Sensor DTCs P0122 or P0123.

^ No Vehicle Speed Sensor (VSS) Assy. DTCs P0502 or P0503.

^ No TCC Sol. Valve DTC P0740.

^ No 1-2 SS Valve DTC P0753.

^ No 2-3 SS Valve DTC P0758.

^ No 3-2 SS Valve Assy. DTC P0785.

^ No TCC PWM Sol. Valve DTC P1860.

^ The engine speed is greater than 450 RPM for 5 seconds.

^ Not in fuel cutoff.

^ The vehicle speed is 56-105 km/h (35-65 mph).

^ The speed ratio is 0.64-0.95 (the speed ratio is the engine speed divided by the output speed).

^ The engine speed is 1500-3500 RPM.

^ The engine torque is 40-450 lbs.ft.

^ The gear range is D4.

^ Not in 1st gear.

^ The Throttle Position (TP) angle is 12-50%.

^ The Transmission Fluid Temperature (TFT) is between 20-130°C (68-266°F).

^ The TCC is commanded On for 5 seconds.

^ The TCC is at maximum duty cycle for 5 seconds.

^ The shift solenoid performance diagnostic counters are zero.

^ TCC slip speed is 300-1000 RPM.

^ All conditions met for 7 seconds.

IMPORTANT: The following actions may occur before the DTC sets.

^ If the TCC is commanded On and at maximum duty cycle for 5 seconds, the TP angle is 7-40%, and the transmission slip counter has incremented to either 1 or 2 (out of 3 to increment the fail counter for the current ignition cycle), then the following slip conditions and actions may increment the fail counter for the current ignition cycle:

These conditions must occur sequentially.

Condition 1

If the TCC slip speed is 200-1000 RPM for 7 seconds, then the PCM will command maximum line pressure and freeze shift adapts from being updated.

Condition 2

If Condition 1 is met and the TCC slip speed is 200-1000 RPM for 7 seconds, then the PCM will command the TCC Off for 1.5 seconds.

Condition 3

If Condition 2 is met and the TCC slip speed is 200-1000 RPM for 7 seconds, then the fail counter on the current ignition cycle is incremented. Two consecutive fail counts are required to set DTC P1870 (type B).

The above slip conditions and actions may be disregarded if the TCC is commanded Off at any time as a result of a driving maneuver (sudden acceleration or deceleration).

ACTION TAKEN WHEN THE DTC SETS

^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

^ The PCM inhibits TCC engagement.

^ The PCM commands maximum line pressure.

^ The PCM inhibits 4th gear if the transmission is in hot mode.

^ The PCM freezes shift adapts from being updated.

^ DTC P1870 stores in PCM history.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The PCM turns OFF the MIL after three consecutive trips without a failure reported.

^ A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

^ 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

Internal transmission failures could set DTC P1870.

TEST DESCRIPTION

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

3. This step tests the torque converter for slippage while in a commanded lock-up state.