DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Input. Chevrolet Malibu 1999

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1999 🢒 Malibu 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T40-E/4T45-E 🢒 DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Input

DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Input 2.4L

Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The automatic transmission output (shaft) speed sensor (A/T OSS) provides vehicle speed information to the PCM. The A/T OSS is a permanent magnet (PM) generator mounted to the transmission case. The PM generator produces an AC voltage as the transmission speed sensor rotor teeth pass through the sensor's magnetic field. 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 MAP DTCs P0107 or P0108.

•	No TP DTCs P0121, P0122, or P0123.

•	No A/T 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%.

•	The MAP is greater than 50 kPa.

•	The input speed is greater than 2,000 RPM.

Conditions for Setting the DTC

The output speed is less than 3.2 km/h (2 mph) 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 shift adapts from being updated.

•	The PCM calculates output speed from input speed, engine speed, and commanded gear.

•	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 clears the DTC from PCM history.

•	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 fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids

•	The condition may be intermittent. Inspect for a loose A/T OSS, or faulty sensor connection.

•	Inspect the wiring at the PCM and at the A/T OSS 2-way connector for the following conditions:

-	A backed out terminal

-	A damaged terminal

-	Reduced terminal tension

-	A chafed wire

-	A broken wire inside the insulation

-	Moisture intrusion

Corrosion

•	When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

•	Inspect for a damaged A/T OSS. Inspect for damaged transmission rotor teeth.

•	A slipping forward clutch could set DTC P0502.

Test Description

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

This step tests the ability of the A/T OSS to produce an AC current. This step also verifies the integrity of the wiring to the PCM.

This step tests the A/T OSS circuit for correct resistance.

DTC P0502 Vehicle Speed Sensor Circuit -- Low Input (2.4L)

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Install the Scan Tool .
Turn the ignition switch to the RUN position.

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.

Record the Freeze Frame and Failure Records.
Clear the DTCs.

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.

Raise and support the drive wheels.
Start and idle the engine.
Place the transmission in DRIVE.

With the drive wheels rotating, does the transmission output speed increase when the wheel speed increases?

Go to Diagnostic Aids

Go to Step 3

Turn the ignition switch OFF.
Disconnect the C1 and C2 PCM connectors.
Using the J 35616-A connector test adapter kit, connect the J 39200 digital multimeter (DMM) between PCM terminals C1-64 and C2-61.
Select AC volts.
Turn the ignition switch to the RUN position.
Rotate the right front drive wheel by hand.
Observe the DMM display.

Can a voltage greater than the specified value be obtained?

0.5 V AC

Go to Step 15

Go to Step 4

Select ohms on the DMM in order to measure circuit resistance.

Is the circuit resistance within the specified range?

1,530 - 1,870 ohms

Go to Step 8

Go to Step 5

Is the circuit resistance greater than the specified value?

1,870 ohms

Go to Step 11

Go to Step 6

Leave the DMM test leads connected.
Disconnect the A/T OSS connector at the transmission.

Is the circuit resistance less than the specified value?

1,530 ohms

Go to Step 7

Go to Step 14

Inspect circuits 400 and 401 for being shorted together.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Go to Step 13

Inspect circuit 400 for a short to ground.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Go to Step 13

Go to Step 9

Reconnect the C1 and C2 PCM connectors.
Select DC volts.
Using the J 35616-A connector test adapter kit, connect the DMM test leads to terminals A and B of the A/T OSS connector end.
Turn the ignition switch to the RUN position.

Does the DMM display system voltage?

Go to Step 10

Go to Step 12

Inspect circuit 400 for a short to power.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Go to Step 13

Inspect circuit 400 for an open.
Inspect circuit 401 for an open.

Refer to General Electrical Diagnosis in Wiring Systems.

Was a condition found?

Go to Step 13

Go to Step 14

Remove the A/T OSS. Refer to Vehicle Speed Sensor Replacement .
Inspect the A/T OSS and the transmission for the following:

•	Incorrect A/T OSS

•	A/T OSS damage

•	Excessive A/T OSS to speed sensor rotor gap

•	Incorrect speed sensor rotor alignment

•	Speed sensor rotor damage

Repair any of the above items as necessary

Is the repair complete?

Go to Step 16

Repair the wiring as necessary.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Step 16

Replace the A/T OSS.

Refer to Vehicle Speed Sensor Replacement .

Is the replacement complete?

Go to Step 16

Replace the PCM.

Refer to Powertrain Control Module Replacement/Programming in Engine Controls.

Is the replacement complete?

Go to Step 16

Perform the following procedure in order to verify the repair:

Select DTC.
Select Clear Info.
Operate the vehicle at a speed greater than 3 km/h (2 mph) for 3 seconds.
Select Specific DTC.
Enter DTC P0502.

Has the test run and passed?

System OK

Go to Step 1

DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Input 3.1L

Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

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 A/T ISS DTCs P0716 or P0717.

•	No engine torque DTC P1644.

•	No TFP manual valve position switch DTC P1810.

•	The transmission is in a drive range.

•	The TP angle is greater than 12%.

•	The input speed is greater than 1,500 RPM.

•	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 shift adapts from being updated.

•	The PCM calculates output speed from input speed, engine speed and commanded gear.

•	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 clears the DTC from PCM history.

•	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 fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids

•	The condition may be intermittent. Inspect for a loose A/T OSS, or faulty sensor connection.

•	Inspect the wiring at the PCM and at the A/T OSS 2-way connector for the following conditions:

-	A backed out terminal

-	A damaged terminal

-	Reduced terminal tension

-	A chafed wire

-	A broken wire inside the insulation

-	Moisture intrusion

Corrosion

•	When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

•	Inspect for a damaged A/T OSS. Inspect for damaged transmission rotor teeth.

•	A slipping forward clutch could set DTC P0502.

Test Description

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

This step tests the ability of the A/T OSS to produce an AC current. This step also verifies the integrity of the wiring to the PCM.

This step tests the A/T OSS circuit for correct resistance.

DTC P0502 Vehicle Speed Sensor Circuit -- Low Input (3.1L)

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Install the Scan Tool .
Turn the ignition switch to the RUN position.

Record the Freeze Frame and Failure Records.
Clear the DTCs.

Raise and support the drive wheels.
Start and idle the engine.
Place the transmission in DRIVE.

With the drive wheels rotating, does the transmission output speed increase when the wheel speed increases?

Go to Diagnostic Aids

Go to Step 3

Turn the ignition switch OFF.
Disconnect the C1 PCM connector.
Using the J 35616-A connector test adapter kit, connect the J 39200 digital multimeter (DMM) between PCM terminals C1-64 and C1-65.
Select AC volts.
Turn the ignition switch to the RUN position.
Rotate the right front drive wheel by hand.
Observe the DMM display.

Can a voltage greater than the specified value be obtained?

0.5 V AC

Go to Step 15

Go to Step 4

Select ohms on the J 39200 DMM in order to measure circuit resistance.

Is the circuit resistance within the specified range?

1,530 - 1,870 ohms

Go to Step 8

Go to Step 5

Is the circuit resistance greater than the specified value?

1,870 ohms

Go to Step 11

Go to Step 6

Leave the J 39200 DMM test leads connected.
Disconnect the A/T OSS connector at the transmission.

Is the circuit resistance less than the specified value?

1,530 ohms

Go to Step 7

Go to Step 14

Inspect circuits 400 and 401 for being shorted together.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Go to Step 13

Inspect circuit 400 for a short to ground.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Go to Step 13

Go to Step 9

Reconnect the C1 PCM connector.
Select DC volts.
Using the J 35616-A , connect the J 39200 DMM test leads to terminals A and B of the A/T OSS connector end.
Turn the ignition switch to the RUN position.

Does the DMM display system voltage?

Go to Step 10

Go to Step 12

Inspect circuit 400 for a short to power.

Refer to General Electrical Diagnosis in Wiring Systems.

Was the condition found?

Go to Step 13