GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Yukon XL - 4WD 🢒 DTC 🢒 DTC P0894

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

Circuit Description

The powertrain control module (PCM) monitors the engine speed, and the transmission output shaft speed. The PCM calculates turbine shaft speed and torque converter clutch (TCC) slip speed by using inputs from the automatic transmission input shaft speed sensor (AT ISS), automatic transmission output shaft speed sensor (AT OSS), and other transmission components. The forward clutch housing is used as the AT 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 PCM detects an excessive TCC slip speed in D4 OVERDRIVE, when the TCC should be engaged, DTC P0894 sets. DTC P0894 is a type C DTC. For California emissions vehicles, DTC P0894 is a type B DTC.

Conditions for Running the DTC
    • No MAF sensor DTCs P0101, P0102 or P0103.
    • No MAP sensor DTCs P0106, P0107 or P0108.
    • No TP sensor DTCs P0120 or P0220.
    • No AT VSS DTC P0502 or P0503.
    • No AT ISS DTCs P0716 or P0717.
    • No TCC PWM solenoid valve DTCs P0741, P0742 or P2761.
    • No TCC Stuck ON DTC P0742.
    • No TCC Stuck OFF DTC P0741.
    • No TCC electrical DTC P0753 or P0758.
    • No 1-2 SS valve DTCs P0751, P0752 or P0753.
    • No 2-3 SS valve DTCs P0756, P0757 or P0758.
    • No TFP manual valve position switch DTCs P1810.
    • The TP sensor is 10-100 percent.
    • Engine speed is 1,250-5,000 RPM .
    • The TFT is 20-130°C (68-266°F).
    • Vehicle speed is 56-177 km/h (35-110 mph).
    • TFP manual valve position switch indicates D4.
    • Speed ratio is 2.25-0.70.
    • The engine torque must be between 108 N·m (80 lb ft) and:
       - 6.0L: 542 N·m (400 lb ft)
       - 8.1L: 881 N·m (650 lb ft)
    • The TCC is commanded ON for 0.04 second or more.
    • TCC is locked ON for greater than 0.1 second.
    • The PCM commands 4th gear.

Conditions for Setting the DTC

The PCM detects slip in the torque converter clutch and/or the fourth gear clutch pack with the TCC in an apply or locked mode. DTC P1870 sets during the second consecutive trip when one of the following conditions occur:

Condition 1

The TCC slip speed is 100-550 for 10 seconds for three occurrences.

Condition 2

    • The TCC slip speed is 100-550 for 10 seconds, the PCM commands maximum line pressure.
    • The TCC slip speed is 100-550 for 12.5 seconds, the PCM commands the TCC Off for 2 seconds.
    • The TCC slip speed is 100-550 for 15 seconds.

Action Taken When the MIL/DTC Sets
    • For California emission equipped vehicles, the PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. For Federal emission equipped vehicles, the MIL is not illuminated.
    • The PCM commands maximum line pressure.
    • The PCM inhibits the TCC engagement.
    • The PCM freezes transmission adaptive functions.
    • The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame, California only, and Failure Records, California and Federal.
    • The PCM stores the DTC P0894 in PCM history during the second consecutive trip, California, or the first trip, Federal, in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
    • For California emissions, the PCM 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.
    • For California emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.
    • For Federal emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.
    • The PCM 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 PCM.

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(s)

Yes

No

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls - 6.0L or Diagnostic System Check - Engine Controls in Engine Controls - 8.1L

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 Freeze Frame and Failure Records. Using the Clear Info Function erases the Freeze Frame and Failure Records from the PCM.

  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.

    7. 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 20-130°C (50-266°F).
    • The transmission is in D4.
    • The TCC duty cycle is greater than 80%.
    • The TP angle is 10-80%.

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 10-80%.

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 greater than 80%.
    • The TP angle is 10-80%.

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 gauge to the transmission line pressure tap.
  2. Perform the Line Pressure Check Procedure.

Refer to Line Pressure Check .

Is the line pressure within specifications?

--

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
    • Refer to Turbine Shaft Disassemble in Transmission Unit Repair Manual.
    • Converter limit valve plug leaking
    • Refer to Transmission Fluid Pump Disassemble in Transmission Unit Repair Manual.
    • TCC PWM solenoid valve mechanically stuck OFF
    • TCC regulator apply valve stuck in the released position
    • Refer to Control Valve Body Cleaning and Inspection in Transmission Unit Repair Manual.
  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
    • Refer to Forward Clutch Assembly Disassemble in Transmission Unit Repair Manual.
    • Overrun clutch plates damaged or burned
    • Refer to Clutch Plate Diagnosis .
    • Overdrive clutch roller assembly not holding
    • Refer to Overrun Clutch Assembly Disassemble in Transmission Unit Repair Manual.
  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 20-130°C (50-266°F).
    • Drive the vehicle in 4th gear, with the TCC commanded ON.
    • The TP angle is 10-100%.
    • TCC slip speed must be -25 to +25 RPM for 10 seconds.
  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 in Engine Controls - 6.0L or Diagnostic Trouble Code (DTC) List in Engine Controls - 8.1L

System OK