GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Avalanche - 4WD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - 4L80-E/4L85-E 🢒 DTC P0894

Object Number: 199389 Size: LF
Master Electrical Component List
Automatic Transmission Controls Schematics

Circuit Description

The transmission control module (TCM) monitors the engine speed, and the transmission output shaft speed. The TCM calculates turbine shaft speed and torque converter clutch (TCC) slip speed by using inputs from the automatic transmission input shaft speed sensor (AT ISS), the automatic transmission output shaft speed sensor (AT OSS), and other transmission components. The forward clutch housing is used as the ISS rotor. Whenever the TCC is engaged, engine speed and turbine speed will closely match, indicating low TCC slip speed. In D3 with the TCC engaged, calculated transmission component slip can only occur in the torque converter. In D4 OVERDRIVE with the TCC engaged, transmission component slip can occur in the TCC or the fourth clutch assembly.

If the TCM detects an excessive TCC slip speed in D4 OVERDRIVE, when the TCC should be engaged, then DTC P0894 sets. DTC P0894 is a type B DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0894 Transmission Component Slipping

Conditions for Running the DTC
    • No transmission ISS DTCs P0716 or P0717.
    • No transmission OSS DTC P0722, or P0723.
    • No TCC PWM solenoid valve performance DTCs P0741 or P0742.
    • No 1-2 SS valve DTCs P0751 or P0752.
    • No 2-3 SS valve DTCs P0756 or P0757.
    • No 1-2 SS valve electrical DTCs P0973 or P0974.
    • No 2-3 SS valve electrical DTCs P0976 or P0977.
    • No TFP manual valve position switch DTCs P1810, P1816 or P1818.
    • No TCC PWM electrical DTCs P2763 or P2764.
    • The engine is running for 5 seconds or greater.
    • The TFT is between 20-130°C (68-266°F).
    • Vehicle speed is above 48 km/h (30 mph).
    • TFP manual valve position switch indicates D4.
    • The calc. throttle position is 8 percent or greater.
    • Speed ratio is 2.25-0.70.
    • The engine torque is greater than 50 N·m (37 lb ft).
    • The TCC is commanded ON at 65 percent duty cycle or greater for 5 seconds or greater.
    • TCC is locked ON for greater than 0.1 second.

Conditions for Setting the DTC

The TCM detects slip in the torque converter clutch and/or the fourth gear clutch pack with the TCC in an apply or locked mode. DTC P0894 sets during the second consecutive trip when one of the following conditions occur:

Condition 1

The TCC slip speed is between 100 RPM and 1500 RPM for 10 seconds or more for 3 occurrences.

Condition 2

The following sequence of events occur:

    • The TCC slip speed is between 100 RPM and 1500 RPM for 10 seconds or greater, the TCM commands maximum line pressure and freezes adapts.
    • The TCC slip speed is between 100 RPM and 1500 RPM for 10 seconds or greater, the TCM commands the TCC OFF for 1.5 seconds or greater and freezes adapts.
    • The TCC slip speed is between 100 RPM and 1500 RPM for 10 seconds or greater.

Action Taken When the MIL/DTC Sets
    • The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
    • The TCM commands maximum line pressure.
    • The TCM forces the TCC off.
    • The TCM inhibits TCC engagement.
    • The TCM inhibits 4th gear if the transmission is in Hot Mode.
    • The TCM freezes transmission adaptive functions.
    • The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
    • The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
    • The TCM stores the DTC P0894 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
    • The ECM turns OFF the MIL during the third consecutive drive trip in which the TCM does not send a MIL illumination request.
    • A scan tool can clear the MIL/DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the TCM.

Diagnostic Aids
    • A TFP manual valve position switch malfunction can set DTC P0894.
    • A mechanical failure of the shift solenoids or TCC PWM solenoid valve can set DTC P0894.
    • Internal transmission failures can result in a DTC P0894.
    • Sticking or contaminated shift valves may cause intermittent slipping in D4.
    • DTC P0894 defaults to an elevated line pressure condition which may result in partial TCC apply. This may produce an idle surge that could stall the engine.

Test Description

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

  1. This step tests the indicated range signal to the actual selected range. A faulty TFP manual valve position switch can set a DTC P0894.

    2.

  2. This step tests for excessive TCC slip speed while in a commanded TCC lock-up state and in fourth gear; and confirms that the fault is present.

    3.

  3. This step tests for excessive TCC slip speed while in a commanded TCC lock-up state and in third gear.

  4. This step tests for a sticking TCC shift valve.

    5.

  5. This step tests for proper transmission line pressure.

Step

Action

Value

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Perform the Transmission Fluid Checking Procedure. Refer to Transmission Fluid Check .

Did you perform the Transmission Fluid Checking Procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. Important: Before clearing the DTCs, use the scan tool in order to record the ECM and TCM Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the ECM and TCM.

  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTCs.
  5. With the engine idling and at normal operating temperature, apply the brake pedal.
  6. Select each transmission range: D1, D2, D3, D4, N, R, and P. Refer to Transmission Fluid Pressure Manual Valve Position Switch Logic .

Does each selected transmission range match the scan tool TFP switch A/B/C display?

--

Go to Step 4

Go to DTC P1810

4

Drive the vehicle under the following conditions:

    • The TFT is between 20-130°C (50-266°F).
    • The transmission is in D4.
    • The TCC duty cycle is 65% or greater.
    • The calc. throttle position is 8% or greater.

At any time is the TCC slip speed greater than the specified value for 10 seconds?

120 RPM

Go to Step 5

Go to Diagnostic Aids

5

Drive the vehicle under the following conditions:

    • The transmission is in D3.
    • Command the TCC ON with the scan tool.
    • The TP angle is 8% or greater.

At any time is the TCC slip speed greater than the specified value for 10 seconds?

120 RPM

Go to Step 7

Go to Step 6

6

Repeat the procedure in Step 4. Drive the vehicle under the following conditions:

    • The transmission is in D4.
    • The TCC duty cycle is 65% or greater.
    • The calc. throttle position is 8% or greater.

Is the TCC slip speed greater than the specified value?

120 RPM

Go to Step 8

Go to Diagnostic Aids

7

  1. Connect the J 21867 pressure gage to the transmission line pressure tap.
  2. Perform the Line Pressure Check Procedure. Refer to Line Pressure Check .

Were the line pressures within specifications during the Line Pressure Check Procedure?

--

Go to Step 8

Go to Symptoms - Automatic Transmission

8
  1. Inspect the transmission for the following conditions:
    2. • TCC enable valve mechanically stuck OFF
    • TCC solenoid valve O-ring seals worn
    • TCC shift valve stuck in the released position
    • Turbine shaft oil holes plugged
    • Turbine shaft seals leaking
    • Converter limit valve plug leaking
    • TCC PWM solenoid valve mechanically stuck OFF
    • TCC regulator apply valve stuck in the released position
  2. Repair the condition as necessary.

Did you complete the repair?

--

Go to Step 10

Go to Step 9

9
  1. Inspect the transmission for the following conditions:
    2. • Fourth clutch plates damaged or burned
    • Refer to Clutch Plate Diagnosis .
    • Fourth clutch piston seals leaking
    • Fourth clutch cup plug leaking
    • Fourth clutch retainer ring not seated
    • Overrun clutch plates damaged or burned
    • Refer to Clutch Plate Diagnosis .
    • Overdrive clutch roller assembly not holding
  2. Repair the condition as necessary.

Did you complete the repair?

--

Go to Step 10

--

10

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • Ensure that TFT is between 20-130°C (50-266°F).
    • Drive the vehicle in 4th gear, with the TCC commanded ON.
    • The calc. throttle position is 8% or greater.
    • The TCM must see a TCC Slip Speed of -20 to +40 RPM for 6 seconds or greater.
  4. Select Specific DTC.
  5. Enter DTC P0894.

Has the test run and passed?

--

Go to Step 11

Go to Step 2

11

With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK