GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Malibu 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC P0502

Object Number: 650094 Size: SF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The automatic transmission output shaft speed sensor (AT OSS) provides vehicle speed information to the PCM. The AT OSS is a permanent magnet generator mounted to the transmission case. The AT OSS produces an AC voltage as the transmission speed sensor rotor teeth pass through the magnetic field of the sensor. The AC voltage level increases as the speed of the vehicle increases. The PCM converts the AC voltage into a digital signal. The PCM uses the vehicle speed signal to determine shift timing, torque converter clutch (TCC) apply, TCC release, and gear ratio calculations.

When the PCM detects a low output speed and the vehicle has a large engine speed in a drive gear, then DTC P0502 sets. DTC P0502 is a type B DTC.

Conditions for Running the DTC
    • No TP DTCs P0121, P0122, or P0123.
    • No MAP DTCs P0107 or P0108.
    • No AT ISS DTCs P0716 or P0717.
    • No TFP manual valve position switch DTC P1810.
    • The transmission is in a drive range.
    • The TP angle is greater than 12 percent.
    • The input speed is greater than 1,500 RPM.
    • The engine torque is greater than 68 N·m (50 lb ft).

Conditions for Setting the DTC

The output speed is less than 150 RPM for 3 seconds.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
    • The PCM commands maximum line pressure.
    • The PCM freezes transmission adapt functions.
    • The PCM calculates output speed from input speed, engine speed, and commanded gear.
    • The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
    • The PCM stores DTC P0502 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

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 can clear the MIL/DTC.
    • The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
    • The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.

Test Description

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

  1. This step tests the ability of the AT OSS to produce an AC voltage. This step also verifies the integrity of the wiring to the PCM.

    2.

  2. This step tests the AT OSS circuit for correct resistance.

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls

2

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

    3. Important: Before clearing the DTC, 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 DTC Freeze Frame and Failure Records.
  4. Clear the DTC.

    5. Notice: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel.

  5. Raise and support the drive wheels.
  6. Start and idle the engine.
  7. Place the transmission in DRIVE.
  8. Select Transmission OSS on the scan tool.

With the drive wheels rotating, does Transmission OSS increase when the wheel speed increases?

--

Go to Intermittent Conditions in Engine Controls

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1.
  3. Using the J 35616 connector test adapter kit, connect the DMM between PCM terminals C1-64 and C1-65.
  4. Select AC volts on the DMM.
  5. Turn ON the ignition, with the engine OFF.
  6. Rotate the right front drive wheel by hand.
  7. Observe the DMM display.

Can a voltage greater than the specified value be obtained?

0.5 V AC

Go to Step 14

Go to Step 4

4

  1. Leave the DMM test leads connected.
  2. Measure circuit resistance.

Is the circuit resistance within the specified range?

1,530-1,870 ohms

Go to Step 8

Go to Step 5

5

Is the circuit resistance greater than the specified value?

1,870 ohms

Go to Step 11

Go to Step 6

6

  1. Leave the DMM test leads connected.
  2. Disconnect the AT OSS connector at the transmission.

Is the circuit resistance less than the specified value?

1,530 ohms

Go to Step 7

Go to Step 13

7

Test the high signal circuit (CKT 400) and the low signal circuit (CKT 401) of the AT OSS for being shorted together.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

--

8

Test the high signal circuit (CKT 400) of the AT OSS for a short to ground.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 9

9

  1. Reconnect PCM connector C1.
  2. Select DC volts on the DMM.
  3. Using the J 35616 , connect the DMM test leads to terminals A and B of the AT OSS wiring harness connector end.
  4. Turn ON the ignition, with the engine OFF.

Does the DMM display system voltage?

--

Go to Step 10

Go to Step 12

10

Test the high signal circuit (CKT 400) of the AT OSS for a short to voltage.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

--

11
  1. Test the high signal circuit (CKT 400) of the AT OSS for an open.
  2. Test the low signal circuit (CKT 401) of the AT OSS for an open.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct a condition?

--

Go to Step 15

Go to Step 13

12
  1. Remove the AT OSS.

    2. Refer to Vehicle Speed Sensor Replacement .

  2. Inspect the AT OSS and the transmission for the following conditions:
    3. • Incorrect AT OSS
    • AT OSS damage
    • Excessive AT OSS to speed sensor rotor gap
    • Incorrect speed sensor rotor alignment
    • Speed sensor rotor damage
  3. Repair any of the above conditions as necessary.

Refer to Transmission Overhaul in Transmission Unit Repair Manual.

Did you complete the repair?

--

Go to Step 15

--

13

Replace the AT OSS.

Refer to Vehicle Speed Sensor Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM.

Refer to Powertrain Control Module Replacement in Engine Controls.

Did you complete the replacement?

--

Go to Step 15

--

15

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Drive the vehicle in D4.
  4. The transmission output speed must be greater than 250 RPM for 2 seconds.
  5. Select Specific DTC.
  6. Enter DTC P0502.

Has the test run and passed?

--

System OK

Go to Step 1