Code P1502

Good morning,

Is the ABS light on as well as the check engine light? If it is not, then you need a ECM. The code is for both systems.

https://www.2carpros.com/articles/abs-warning-light-on-easy-repair-guide

Roy

P1502-VEHICLE SPEED SENSOR 1/2 CORRELATION - NON DRIVE WHEELS

P1502 - Vehicle Speed Sensor 1/2 Correlation - Non Drive Wheels
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WHEN MONITORED
Ignition on and vehicle moving. Cruise is learned and customer is trying to use the Cruise.

SET CONDITION
The PCM recognizes rear wheel speed is greater than front wheel speed.

POSSIBLE CAUSES
Vehicle speed signal circuits shorted to voltage
Vehicle speed signal circuits shorted to ground
Tire circumference
PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. ACTIVE DTC
Ignition on, engine not running.
With a scan tool, read DTCs.

Q: Is the DTC active at this time?

YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Perform the POWERTRAIN VERIFICATION TEST. See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test

2. VISUAL INSPECTION

NOTE: This code can set due to tire circumference differences and from the front or rear wheels being on a slippery surface while the opposite tires are not.

This code may also set on a hard acceleration on loose gravel or during other off road driving conditions.
Check tire pressure of all the tires.
Check tire wear on all the tires.
Ask the customer what the road and driving conditions were like when the fault set.

Q: Were any problems found?

YES: Repair as necessary. If the code set during a front OR rear wheel spin condition, no repair is necessary. Perform the POWERTRAIN VERIFICATION TEST. See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > Powertrain Verification Test
NO: Go To 3

3. VSS SIGNAL CIRCUITS SHORTED TO VOLTAGE

CAUTION:
Certain ABS systems rely on having the Powertrain Control Module (PCM) broadcast the Vehicle Identification Number (VIN) over the bus network. To prevent problems of DTCs and other items related to the VIN broadcast, it is recommend that you disconnect the ABS CAB (controller) temporarily when replacing the PCM. Once the PCM is replaced, write the VIN to the PCM using the DRB scan tool. This is done from the engine main menu. Arrow over to the second page to "1. Miscellaneous". Select "Check VIN" from the choices. Make sure it has the correct VIN entered before continuing. When the VIN is complete, turn off the ignition key and reconnect the ABS module connector. This will prevent the setting of DTCs and other items associated with the lack of a VIN detected when you turn the key ON after replacing the PCM.
Use the DRB scan tool to reprogram the new PCM with the vehicles original identification number (VIN) and the vehicles original mileage. If this step is not done, a Diagnostic Trouble Code (DTC) may be set.

REMOVAL

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The PCM (1) is located in the engine compartment attached to the dash panel (3).

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To avoid possible voltage spike damage to the PCM, ignition key must be off, and negative battery cable must be disconnected before unplugging PCM connectors.

1. Disconnect negative battery cable at battery.
2. Remove cover over electrical connectors. Cover snaps onto PCM.
3. Carefully unplug the three 32-way connectors (four 38-way connectors if equipped with NGC) from PCM (1).
4. Remove three PCM mounting bolts (3) and remove PCM from vehicle.

Okay, did you replace the sensors?

https://www.2carpros.com/articles/how-to-replace-an-abs-wheel-speed-sensor

https://www.2carpros.com/articles/abs-wheel-speed-sensor-test

I attached the procedure for you. Retest after your repair to see if it reads correctly.

Roy

SENSOR- WHEEL SPEED-ABS-FRONT

REMOVAL
1. Remove the front rotor.

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2. Remove the wheel speed sensor mounting bolt (1) from the hub (3).
3. Remove the wheel speed sensor (2) from the hub (3).
4. Remove the wiring from the clips and disconnect the electrical connector.

The ones on the transmission have nothing to do with the issue.

Why did you not replace the passenger front? I would replace that. The code says front wheel speed sensor and does not identify which one.

Roy

The information below for you. You should have 3 sensors.

Roy

SENSOR- WHEEL SPEED-ABS-FRONT

DESCRIPTION
The ABS brake system uses 3 wheel speed sensors. A sensor is mounted to each front hub/bearings. The third sensor is mounted on top of the rear axle differential housing.

OPERATION

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The Wheel Speed Sensor consists of a magnet (1) surrounded by windings from a single strand of wire (5). The sensor sends a small AC signal to the ABM. This signal is generated by magnetic induction. The magnetic induction is created when a toothed sensor ring (exciter ring or tone wheel) (4) passes the stationary magnetic WSS.

When the ring gear is rotated, the exciter ring (4) passes the tip of the WSS. As the exciter ring tooth approaches the tip of the WSS, the magnetic lines of force expand, causing the magnetic field to cut across the sensor's windings (5). This, in turn causes current to flow through the WSS circuit in one direction. When the exciter ring tooth moves away from the sensor tip, the magnetic lines of force collapse cutting the winding in the opposite direction. This causes the current to flow in the opposite direction. Every time a tooth of the exciter ring passes the tip of the WSS, an AC signal is generated current. Each AC signal (positive to negative signal or squarewave) is interpreted by the ABM. It then compares the frequency of the sinewave to a time value to calculate vehicle speed. The ABM continues to monitor the frequency to determine a deceleration rate that would indicate a possible wheel-locking tendency.

The signal strength of any magnetic induction sensor is directly affected by:
Magnetic field strength; the stronger the magnetic field, the stronger the signal
Number of windings in the sensor; more windings provide a stronger signal
Exciter ring speed; the faster the exciter ring/tone wheel rotates, the stronger the signal will be
Distance (3) "air gap" between the exciter ring teeth and WSS; the closer the WSS is to the exciter ring/tone wheel, the stronger the signal will be.

The WSS is not adjustable. A clearance specification has been established for manufacturing tolerances. If the clearance is not within these specifications, then either the WSS or other components may be damaged. The clearance between the WSS and the exciter ring is 0.005 - 0.050 inch.

The assembly plant performs a "Rolls Test" on every vehicle that leaves the assembly plant. One of the test performed is a test of the WSS. To properly test the sensor, the assembly plant connects test equipment to the Data Link Connector (DLC). This connector is located to the right of the steering column and attached to the lower portion of the instrument panel. The rolls test terminal is spliced to the WSS circuit. The vehicle is then driven on a set of rollers and the WSS output is monitored for proper operation.

The transmission sensors are input and output speed sensors for the transmission. They have nothing to do with the issue.

Did you just buy the car?

Roy

It sounds like the missing sensor is the issue. Look around for the harness for the connection.

Roy