bobgodd

I keep throwing C1287 and C1288. The car is an 02 Z and this is what I find for C1287: Steering Sensor Rate Malfunction. What on earth does that mean?

I have one almost bald tire on the right rear vs the left rear is almost brand new, and I thought that the slipping might cause the TCS to throw a code, but seeing the steering sensor thingy, I'm a bit lost now.

Any idears?

Rob

Bill Dearborn

Here is a description of the parts that are used in the ABS/TC/AH system you have in the car.

This vehicle is equipped with the Delco/Bosch 5.3 antilock braking system.

The vehicle is equipped with the following braking systems:

Antilock Brake System (ABS)
Dynamic Rear Proportioning (DRP)
Traction Control System (TCS)
Vehicle Stability Enhancement System (VSES) (w/JL4)
The following components are involved in the operation of the above systems:

Electronic Brake Control Module (EBCM) - The EBCM controls the system functions and detects failures. The EBCM contains the following components:
System Relay - The system relay is energized when the ignition is ON and no ABS DTCs are present. It supplies battery positive voltage to the solenoid valves and pump motor.
Vent Tube - The vent tube, located in the EBCM connector, is an opening to the internal cavity of the EBCM. It allows ventilation of the EBCM internals.
Brake Pressure Modulator Valve (BPMV) - The BPMV contains the hydraulic valves and pump motor that are controlled electrically by the EBCM. The BPMV uses a 4 circuit configuration with a front/rear split. The BPMV directs fluid from the reservoir of the master cylinder to the front wheels and fluid from the other reservoir to the rear wheels. The circuits are hydraulically isolated so that a leak or malfunction in one circuit will allow continued braking ability on the other.

Important
There is a rubber isolator located under the BPMV and on the mounting studs. The rubber isolators protect the BPMV and the EBCM from vehicle vibrations.


The BPMV contains the following components:
Pump Motor
Inlet Valves (one per wheel)
Outlet Valves (one per wheel)
Master Cylinder Isolation Valves (one per drive wheel)
Prime Valves (one per drive wheel)
Wheel Speed Sensors (WSS) - As the wheel spins, the wheel speed sensor produces an AC signal. The EBCM uses this AC signal to calculate wheel speed. The wheel speed sensors are replaceable only as part of the wheel hub and bearing assemblies.
Traction Control Switch - The TCS is manually disabled or enabled using the traction control switch.
Stoplamp Switch - The EBCM uses the stoplamp switch as an indication that the brake pedal is applied.
Lateral Accelerometer Sensor (w/JL4) - The EBCM uses the lateral accelerometer sensor as an indication of the lateral acceleration of the vehicle.
Yaw Rate Sensor (w/JL4) - The EBCM uses the yaw rate sensor as an indication of the yaw rate of the vehicle.
Steering Wheel Position Sensor (SWPS) (w/JL4) - The EBCM uses the SWPS as an indication of the position and rotation of the steering wheel.
Brake Fluid Pressure Sensor (w/JL4) - The brake fluid pressure sensor is attached to the BPMV. The EBCM uses the brake fluid pressure sensor as an indication of the brake fluid pressure in the BPMV.

The steering sensor is located at the base of the steering shaft. Have you had any work done on the car recently? Sometimes mechanics remove the steering shaft from the rack so they can work on the car and do not realize the wheel cannot be turned while it is disconnected.

DTC C1287 or C1288
Circuit Description
The vehicle stability enhancement system (VSES) is activated by the electronic brake control mdoule (EBCM) calculating the desired yaw rate and comparing it to the actual yaw rate input. The desired yaw rate is calculated from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between the desired yaw rate and actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM will attempt to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel.

The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error. The side slip rate error is a function of the lateral acceleration minus the product of the yaw rate and vehicle speed. The yaw rate error and side slip rate error are combined to produce the total delta velocity error. When the delta velocity error becomes too large and the VSES system activates, the drivers steering inputs combined with the differential braking will attempt to bring the delta velocity error toward zero.

The VSES activations generally occur during aggressive driving, in the turns or bumpy roads without much use of the accelerator pedal. When braking during VSES activation, the brake pedal will feel different than the ABS pedal pulsation. The brake pedal pulsates at a higher frequency during VSES activation.

Conditions for Running the DTC
The ignition is ON.

Conditions for Setting the DTC
C1287
One of the following conditions exists:

The steering wheel position sensor is synchronized and the steer rate (speed that the steering wheel appears to be turning) is greater than 1100 degrees/second.
The steer rate is less than 80 degrees/second and the difference in the phase angle between Phase A and Phase B is greater than 20 degrees.
The 2 steering sensor signals (Phase A and Phase B) do not agree for 1 second. Under this condition, this DTC will set along with DTC C1281.
C1288
One of the following conditions exists:

Both Phase A and Phase B are greater than 4.9 volts for 1.6 seconds.
Both Phase A and Phase B are less than 0.2 volts for 1.6 seconds.
The difference in the changes in Phase A and Phase B is greater than 35.2 degrees for 9.76 milliseconds.
Action Taken When the DTC Sets
The EBCM disables the VSES for the duration of the ignition cycle.
The Traction Control and Active Handling indicator turns ON.
The DIC displays the Service Active Handling message.
The ABS remains functional.

Here are some things to check:
Make sure ground points are clean and free of corrosion.

Test the 5 volt reference circuit of the steering wheel position sensor (SWPS) for the following conditions:

An open
A short to ground
A high resistance

Test the signal A circuit of the steering wheel position sensor (SWPS) for the following conditions:

An open
A short to ground
A high resistance

Test the signal B circuit of the steering wheel position sensor (SWPS) for the following conditions:

An open
A short to ground
A high resistance

Inspect for poor connections at the harness connector of the steering wheel position sensor (SWPS).

Inspect for poor connections at the harness connector of the EBCM.

Bill

bobgodd

No work has recently been performed. Only one thing I can think of that was different from the normal routine. I had gotten an oil change at a place that has a slot in the floor for the lube tech and you just drive your car over. Well the ground was a little slopped on the way out of the drive, and my car is lowered, so a good portion of the underside scraped on the lip of the slot. Around the same time that happened, I noticed that I started getting the codes, and also, my cruise control will disengage itself while driving. Any chance those factors could be related?


I think I can handle the testing.. But I may have missed something: where would I find the actual signal A and signal B circuit? You wouldn't happen to have a diagram of the sensor, or at least some wire colors?

I have checked, cleaned, and protected the ground points by the headlights, but haven't gotten around to the others yet, mostly because there was no clear picture of the location. Could these be the correct ground points, or does another ground serve for the sensor circuit?


Thanks for all your help!
Rob

bobgodd

Also, my Active Handling comes on at random times, mostly on the highway. Even when there is nothing wrong with the road, that's what led me to believe that the bald tire had something to do with it.

Any thoughts?

Bill Curlee

Rob

The steering wheel position sensor at the base of your steering column isnt functioning correctly. Is your steering wheel centered/straigt when your going straight down the road??

Seeing both 1287 &1288, I would have to say, its a wiring/connector or voltage issue.

The only two components involved in this error is te EBTCM and the Steering Wheel position sensor.. Check the plug at the EBTCM and sensor.

BC

bobgodd

For the most part, it appears to be straight. I will check the sensor but it would be helpful if I knew what I was checking (ie: yellow wire for 5v or green wire for ground) for.

Also, is this sensor actually located inside the car, or on the steering shaft under the hood? Thanks!

Rob

jjk2509

I have the same problem with may car. Here is a link to an earlier thread I started. This will give another explanation on what wire and how to test.

My question is how do you test the middle blue wire with the volt meter. Do you need to stick the positive wire from the meter inside of the plastic connector on the steering sensor and the black wire to ground?

Thanks in advance for any help.

http://forums.corvetteforum.com/show....php?t=1643998

Bill Curlee

Rob

Thats easy! Most of the time that I go into a 3 page write up about technical stuff only to find out the person who I'm writing to has NO idea what a meter is, what an OHM is or what a screw driver is for!

I can work up a tech procedure for you to follow Us 02 ZO6 guys need to stick together :

The sensor inside the drivers foot well at the base of the steering column and has FOUR wires:

There connected to pins 1, 2, 5 & 6 on the sensor.

Pin 1 is GRY and it will have a 5 VDC (4.9) reference sig from the EBCM. It also feeds the YAW rate sensor and the lateral rate sensor. i would also check for the voltage there. It is also a GRY wire.

Pin 2 is ORN/BLK and it will have a LOW REFF (sensor ground) Sig. It also goes to the YAW and lateral sensors as the same color wires.

Pin 5 is the Steering wheel position sensor signal phase A. It goes directly to the EBCM Lite green wire

Pin 6 is the Steering wheel position sensor signal phase B. It goes directly to the EBCM Lite Blue wire


If you disconnect the sensor plug, you should read (if i read the procedure correctly) .2 VDC on pin 5 & 6

Read the 5 VDC ref voltage to the Low reff pin 2, orange/blk wire should see 5 VDC. if you measure the low reff pin to ground it should not read any higher than 5 ohms.


If it were me,, I would hook up a jumper wire to pin #1 0n the sensor and when the steering wheel is straight, you should see The same output on pins 5 & 6. As you turn the wheel all the way right and left, you should see one pins voltage smoothly increase while the other one smoothly decreases.

Hope this helps.

BC

Teddy98Z28M6

Just curious if you got the problem fixed? If so, what was the solution?

bobgodd

UPDATE:

Well after reading some of the replies, I went back to look at the car, and the wheel was indeed off center during driving. So I took the car to get an alignment today, and all is well. Normally the code sets off immediately, but so far, no code.

Thanks for the help gentlemen!

Rob