Brake pressure differential switch - c1247. I was out in the car having some fun. We were running around 140 and then layed on the brakes pretty hard. Now the c1247 code is on and the service traction control is coming up. I tried clearing the code in the diagnostic menu on the car, but had no luck. Do I need to have it scanned and then cleared? The brakes all still work great and there are not signs of anything wrong.

 

any one else had this problem??

 

Check the level in your brake fluid reservoir, it is low.

 

It's full. Are there any more ideas as to why it won't clear the code?

 

If the level was low when the warning first came up, then the BRAKE lamp will stay illuminated until the code is cleared manually (Either from the DIC or with a scan tool).

If the fluid was full at the time of the warning, then the fluid level switch, or the wiring, has a problem.

The switch is located at the bottom of the reservoir, and you can see the wiring going to it.

Disconnect the wiring at the switch and then try to clear the DTC. If it clears, then the switch is the likely problem. If it doesn't clear, there is a problem in the wiring.

 

Thanks for the help. I really appreciate it!!!

 

Well I finally had time to mess with the car. I checked the fluid level again and unplugged the sensor. The service traction control, service active handling and the brake light are still one. The same code C1247 still comes up in the DIC. Any ideas or should I just replace the brake differential switch?

 

Any ideas?

 

What year car do you have? This code has two different diagnostic procedures depending on whether the car is pre or post 2001.

Here are the two procedures:

Pre 2001
DTC C1247 Brake Pressure Differential Switch Activated

Circuit Description
The EBCM monitors the Brake Pressure Differential Switch to turn off Traction Control and Active Handling if a pressure loss is detected in the hydraulic brake system.

Conditions for Setting the DTC
DTC C1247 can be set anytime, if the EBCM detects the Brake Pressure Differential Switch has been grounded due to loss of brake pressure or a short to ground.

Action Taken When the DTC Sets
TCS/Active Handling are disabled.

Indicators that turn on:
RED Brake Warning indicator
Car Icon (TCS indicator)
Messages displayed on the DIC:
Service Traction System
Service Active HNDLG
Conditions for Clearing the DTC
Condition for DTC is no longer present and scan tool clear DTC function is used.
Fifty ignition cycles have passed with no DTCs detected.
Diagnostic Aids
DTC C1247 could be set during a hydraulic brake system bleeding procedure if the ignition switch is in the ON position.
It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.
An intermittent malfunction can be caused by poor connections, broken insulation, or a wire that is broken inside the insulation.
If an intermittent malfunction exists refer to Intermittents and Poor Connections in Wiring Systems.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.

This step checks for a short to ground in the Brake Pressure Differential Switch circuit.

This step indicates that the Brake Pressure Differential Switch circuit is operating properly, and the cause of the DTC is a failure in the hydraulic brake system.

DTC C1247 Brake Pressure Differential Switch Activated Step
Action
Value(s)
Yes
No

1
Was the Diagnostic System Check performed?
--
Go to Step 2
Go to Diagnostic System Check - ABS

2
Turn the ignition switch to the OFF position.
Disconnect the Brake Pressure Differential Switch connector.
Turn the ignition switch to the ON position, engine off.
Does the Red BRAKE Warning Indicator remain on?
--
Go to Step 3
Go to Step 4

3
Repair circuit 1659 for a short to ground. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?
--
Go to Diagnostic System Check - ABS
--

4
The Brake Pressure Differential Switch is working properly. Refer to Hydraulic Brake Diagnostic System Check in Brakes.

Is the repair complete?
--
Go to Diagnostic System Check - ABS
--

Post 2001

DTC C1247
Circuit Description
The brake fluid level switch monitors the level of brake fluid in the master cylinder. When the IPC sees the brake fluid level switch input grounded, it turns ON the red Brake indicator and sends a serial data message to the EBCM that tells the EBCM that the brake fluid level is low.

Conditions for Running the DTC
The ignition is ON.

Conditions for Setting the DTC
The EBCM receives a serial data message from the IPC indicating that the brake fluid level is low.

Action Taken When the DTC Sets
The EBCM disables the TCS/VSES until the DTC becomes a history DTC.
The red Brake warning indicator turns ON.
The Traction Control and Active Handling indicator turns ON.
The DIC displays the following messages:
Low Brake Fluid
Service Traction System
Service Active Handling
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
Inspect the master cylinder reservoir for the proper brake fluid level.

Step
Action
Yes
No

Schematic Reference: Brake Warning System Schematics

Connector End View Reference: Hydraulic Brakes Connector End Views or Instrument Panel, Gages, and Console Connector End Views

1
Did you perform the Hydraulic Brake Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - Hydraulic Brakes

2
Inspect the brake fluid level.

Is the brake fluid level OK?
Go to Step 3
Go to Brake Fluid Loss

3
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Brake Fluid Level parameter in the Instrument Panel Cluster data list.
Does the scan tool indicate that the Brake Fluid Level parameter is OK?
Go to Testing for Intermittent and Poor Connections in Wiring Systems
Go to Step 4

4
Turn OFF the ignition.
Disconnect the brake fluid level switch.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the Brake Fluid Level parameter.
Does the scan tool indicate that the Brake Fluid Level parameter is OK?
Go to Step 6
Go to Step 5

5
Test the signal circuit of the brake fluid level switch 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 10
Go to Step 7

6
Inspect for poor connections at the harness connector of the brake fluid level switch. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 10
Go to Step 8

7
Inspect for poor connections at the harness connector of the instrument cluster (IPC). Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 10
Go to Step 9

8
Replace the brake fluid level switch. Refer to Master Cylinder Fluid Level Sensor Replacement .

Did you complete the repair?
Go to Step 10
--

9
Replace the instrument cluster (IPC). Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gauges and Console.

Did you complete the repair?
Go to Step 10
--

10
Operate the system in order to verify the repair.

Did you correct the condition?
System OK
Go to Step 2

Just reseting the code is not going to solve anything. Good Luck diagnosing the problem.

Bill

 

The car is a 99 model.

 

Use the pre 2001 diagnostic shown above and check the brake pressure differential switch and its wiring as discussed in the diagnostic.

The Brake Pressure Differential Switch (JL4) is attached to the side of the brake combination valve, left front of master cylinder.

The schematic you need to check the wiring is:

 

Well I tried unhooking the switch again and reseting the code. This time with the switch unhooked the code cleared and everything went back to normal. Hooked the switch back up and the code came back on. Looks like I will be replacing the switch.