I am getting this code, DTC C1284 Lateral Accelerometer Sensor*** Self Test Malfunction, I think I am going to need to replace this sensor. I read on the forum that this sensor is located in the passenger floorboard. I had an experience yesterday that concerns me. Please read the attached thread from C5 General and let me know what you think.
http://forums.corvetteforum.com/show....php?t=1905650

I am looking for any information to help me cure this problem, because this was an unnerving experience and I would like to keep this from happening again. Thanks

 

ttt

Really need some help here. Thanks

 

Looks like the gurus are off somewhere so I'll offer this. I haven't had this problem so I have no first hand experience fixing it nor do I know what would be the most common problem.

I don't believe I would throw parts at it without diagnosing the problem. Below is the description/diagnosis procedures. The bottom is in table format which doesn't come across on the forum very well. Basically, the top of the table has Step, Action, Values, Yes, No. These are the headers and the info in the tables start at the numbers (1, 2, etc)


I think I would first look for the obvious. Check wiring and connectors. Check grounds. If you've done any work on the car (audio install etc) look for nicked wiring.

Not saying you don't have an accelerometer problem, but I would do the free stuff first.


DTC C1284 or C1285
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
C1284
The EBCM performs 7 different tests to detect a DTC condition. The numbers below correspond to the numbers in Conditions for Setting the DTC.

The lateral accelerometer sensor bias test runs with the ignition ON.
The lateral accelerometer sensor self test runs with the following conditions:
The ignition is ON.
The vehicle is stopped.
The lateral accelerometer sensor jerk test runs with the ignition ON.
The centered lateral accelerometer sensor test runs with the following conditions:
The ignition is ON.
The vehicle is stopped.
The lateral accelerometer sensor isolation test runs with the following conditions:
The ignition is ON.
DTC C1282 is not set.
The yaw rate is less than 8 degrees/second.
The above lateral accelerometer sensor isolation test runs with the VSES active.
The yaw rate sensor and lateral accelerometer sensor uncorrelated test with the following conditions:
The vehicle speed is greater than 10 km/h (6.2 mph) and less than 100 km/h (62 mph).
The centered yaw rate has a value that is positive and is greater than 10 degrees/second
C1285
The ignition is ON.

Conditions for Setting the DTC
C1284
The EBCM performs 7 different tests to detect a DTC condition. The numbers below correspond to the numbers in Conditions for Running the DTC.

The compensated bias value of the lateral accelerometer sensor is greater than 0.3 g.
The lateral accelerometer sensor performs a self test that results in an offset of 0.5 g. The EBCM compares the sensor output during the self test with the output following the test. The DTC sets when the lateral acceleration immediately following the self test is greater than the self test output minus 0.4 g.
The lateral jerk is greater than 16.5 g/second for 0.12 seconds more than 2 times within the ignition cycle.
The lateral acceleration is 0.4 g for 0.25 seconds.
The side slip error is greater than 0.5 g 30 times within a drive cycle.
The side slip error is greater than 0.5 g for 5 seconds. Under this condition, this DTC will set along with DTC C1281.
The oversteer term is negative for 2 seconds. The oversteer term is the yaw rate value times the lateral acceleration value. Under this condition, this DTC will set along with DTC C1281.
C1285
The lateral accelerometer input voltage is less than 0.15 volts or greater than 4.85 volts for 1 second.

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.
Conditions for Clearing the DTC
The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
Diagnostic Aids
The scan tool may display 2 additional characters after the DTC. Take note of the 2 character code and any other DTCs that are set. The 2 character code is an engineering aid used in order to determine the specific criteria which caused the DTC to set.
During diagnosis, park the vehicle on a level surface.
Check the vehicle for proper alignment. The car should not pull in either direction while driving straight on a level surface.
Find out from the driver under what conditions the DTC was set (when the DIC displayed the Service Active Handling message). This information will help to duplicate the failure.
The Snapshot function on the scan tool can help find an intermittent DTC.
Test Description
The numbers below refer to the step numbers on the diagnostic table.

Tests for the proper operation of the circuit in the low voltage range.

Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.

Tests for a short to voltage in the 5 volt reference circuit.

Tests the bias voltage of the lateral accelerometer sensor.

Step
Action
Values
Yes
No

Schematic Reference: ABS Schematics

Connector End View Reference: ABS Connector End Views

1
Did you perform the ABS Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check - ABS

2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Lateral Accelerometer Input parameter in the VSES data list.
Does the scan tool display that the Lateral Accelerometer Input parameter is within the specified range?
0.15-4.85 V
Go to Step 6
Go to Step 3

3
Turn OFF the ignition.
Disconnect the lateral accelerometer sensor connector.
Turn ON the ignition, with the engine OFF.
With the scan tool, observe the Lateral Accelerometer Input parameter.
Does the scan tool display that the Lateral Accelerometer Input parameter is less than the specified value?
0.15 V
Go to Step 4
Go to Step 10

4
Turn OFF the ignition.
Connect a 3 amp fused jumper wire between the 5 volt reference circuit of the lateral accelerometer sensor and the signal circuit of the lateral accelerometer sensor.
Turn ON the ignition, with the engine OFF.
With the scan tool, observe the Lateral Accelerometer Input parameter.
Does the scan tool display that the Lateral Accelerometer Input parameter is greater than the specified value?
4.85 V
Go to Step 5
Go to Step 8

5
Disconnect the fused jumper wire.
Measure the voltage between the 5 volt reference circuit of the lateral accelerometer sensor and the low reference circuit of the lateral accelerometer.
Does the voltage measure less the specified value?
5.1 V
Go to Step 12
Go to Step 7

6
Does the scan tool display that the Lateral Accelerometer Input parameter is within the specified range?
2.3-2.7 V
Go to Diagnostic Aids
Go to Step 11

7
Test the 5 volt reference circuit of the lateral accelerometer sensor 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 16
Go to Step 13

8
Test the 5 volt reference circuit of the lateral accelerometer sensor for the following conditions:

An open
A short to ground
A high resistance
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 16
Go to Step 9

9
Test the signal circuit of the lateral accelerometer sensor for the following conditions:

An open
A short to ground
A high resistance
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 16
Go to Step 13

10
Test the signal circuit of the lateral accelerometer sensor 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 16
Go to Step 13

11
Disconnect the EBCM harness connector.
Install the J 39700 universal pinout box using the J 39700-300 cable adapter to the EBCM harness connector only.
Test the low reference circuit of the lateral accelerometer sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 16
Go to Step 12

12
Inspect for poor connections at the harness connector of the lateral accelerometer sensor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 16
Go to Step 14

13
Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 16
Go to Step 15

14
Replace the lateral accelerometer sensor. Refer to Lateral Accelerometer Replacement .

Did you complete the repair?
--
Go to Step 16
--

15
Replace the EBCM. Refer to Electronic Brake Control Module (EBCM) Replacement .

Did you complete the repair?
--
Go to Step 16
--

16
Clear the DTCs using the scan tool.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
--
Go to Step 2
System OK

 

The accelerometer takes about 10 minutes to replace and costs around $100 (check with Gene www.gmpartshouse.com), I replaced one several months ago so don't quote me on that price.

It is mounted on the passenger side floor directly in front of the seat by the left front seat attach bolt, remove the seat and the door jamb threshold so you can pull the carpeting up. It is actually bonded to the floor so once you get the 2 nuts loose you'll have to break the bond (I used a screewdriver), when I reinstalled mine I did not glue it down to the floor I just secured the 2 nuts and plugged it in and it has been working fine ever since.

 

Thanks for your time and information. I will more closely read your post and see if I can apply this to my situation. Thanks again!