4L60-E / 4L65-E Automatic Transmission

Diagnostic Chart (Part 1 Of 4):

Diagnostic Chart (Part 2 Of 4):

Diagnostic Chart (Part 3 Of 4):

Diagnostic Chart (Part 4 Of 4):

Schematic:

CIRCUIT DESCRIPTION
The Vehicle Control Module (VCM) monitors the difference between engine speed and transmission output speed. In D3 drive range with the 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 +50 RPM.

When the VCM detects excessive TCC slip when the TCC should be engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

CONDITIONS FOR RUNNING THE DTC
^ No TP sensor DTCs P0122 or P0123.
^ No VSS assembly DTCs P0502 or P0503.
^ No TFT sensor DTCs P0711, P0712 or P0713.
^ No TCC solenoid valve DTC P0740.
^ No 1-2 SS valve DTC P0753.
^ No 2-3 SS valve DTC P0758.
^ No TFP manual valve position switch DTC P1810.
^ No TCC PWM solenoid valve DTC P1860.
^ The engine speed is greater than 450 RPM for 5 seconds.
^ The engine is not in fuel cutoff.
^ The engine torque is 50-400 lb ft.
^ The engine vacuum is 0-150 kPa.
^ The TP angle is 9-35%.
^ The vehicle speed is 48-112 km/h (30-70 mph).
^ The engine speed is 1500-3000 RPM.
^ The speed ratio is 0.69-0.88 (speed ratio is engine speed divided by the output speed).
^ The gear range is D4.
^ The commanded gear is not 1st gear.
^ The TFT is 20-130°C (68-266°F).
^ The shift solenoid performance diagnostic counters are zero.

CONDITIONS FOR SETTING THE DTC
DTC P1870 sets if the following conditions occur for three TCC cycles.
^ The TCC is commanded ON for 5 seconds.
^ The TCC is at maximum duty cycle (95%) for 5 seconds.
^ The TCC slip speed is 130-800 RPM for 7 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The VCM illuminates the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
^ The VCM commands maximum line pressure.
^ The VCM inhibits TCC engagement.
^ The VCM inhibits 4th gear if the transmission is in hot mode.
^ The VCM freezes shift adapts from being updated.
^ The VCM records the operating conditions when the Conditions for Setting the DTC are met. The VCM stores this information as Freeze Frame and Failure Records.
^ The VCM stores DTC P1870 in VCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The VCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool can clear the MIL/DTC.
^ The VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The VCM cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS
^ Bronze material found in the transmission oil pan may indicate stator shaft bushing wear. If bushing wear is suspected, inspect the stator shaft and the input (turbine) shaft for damage.
^ Refer to Symptom Diagnosis for more information. Symptom Related Diagnostic Procedures

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 lockup state.