Lbz with on going P0504 and P0703 - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
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Duramax Third Generation: 2006-2007.5 (LBZ & LLY) Discuss the third generation (2006-2007.5 LBZ & LLY) of the 6.6L Duramax diesel engine & associated components. 2006 LLY engine discussion also belongs in this forum due to the similarities of the 2006 LBZ and the 2006 LLY. Engine related discussion ONLY.

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Old 12-20-2016, 06:45 PM   #1 (permalink)
bucksdmax
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Lbz with on going P0504 and P0703

Got an 06 regular cab Wt that keeps throwing p0504 even after changing brake switch. Is there anything else to look for to track down why it keeps throwing this code and are the 2 codes related to each other??

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Old 12-20-2016, 09:53 PM   #2 (permalink)
Ron Nielson
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DTC P0703 indicates that the TCM did not see the proper input signal for service brake status during an acceleration or deceleration cycle. This may indicate an open or short in the TCC brake switch/cruise control release circuit or a faulty stop lamp switch.

  • Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
  • A bent terminal
  • A backed-out terminal
  • A damaged terminal
  • Poor terminal tension
  • A chafed wire
  • A broken wire inside the insulation
  • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
  • You may have to drive the vehicle in order to experience a condition.


DTC P0504
Circuit Description
The engine control module (ECM) monitors the stop lamp switch signal circuit and the torque converter clutch (TCC) brake switch/cruise control release signal circuit every 100 ms. The ECM monitors the status of the stop lamp switch signal circuit and the TCC brake switch/cruise control signal circuit to see if they match when the brake pedal is pressed or released.

DTC Descriptor
This diagnostic procedure supports the following DTC:

DTC P0504 Brake Switch Circuit 1-2 Correlation

Conditions for Running the DTC
The ignition is ON.

Conditions for Setting the DTC
The status of the stop lamp switch input to the ECM, and the TCC brake switch/cruise control input to the ECM do not match for at least 2 seconds continuously, for 10 occurrences. Each time the signals match then do not match a counter increments. When the counter reaches 10 the DTC will set.

Action Taken When the DTC Sets
When DTC P0504 is set the following will occur:

The cruise control is disabled.

The ECM will function as if the brake pedal is not pressed.

The control module stores the DTC information into memory when the diagnostic runs and fails.

The malfunction indicator lamp (MIL) will not illuminate.

The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

Conditions for Clearing the DTC
The DTC will clear when the status of the stop lamp switch input to the ECM, and the TCC brake switch/cruise control input to the ECM match for at least 2 seconds continuously for both the pressed position and the released position.

A current DTC Last Test Failed clears when the diagnostic runs and passes.

A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.

Clear the DTC with a scan tool.

Diagnostic Aids
Aftermarket trailer brake controllers must be disconnected before diagnosing DTC P0504 due to they could result in incorrect diagnostics.

Check for intermittents and poor connections. Refer to Testing for Intermittent Conditions and Poor Connections .

Step
Action
Yes
No

Schematic Reference: Exterior Lights Schematics and Cruise Control Schematics in Cruise Control

Connector End View Reference: Master Electrical Component List in Wiring Systems

1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
Turn the key On, engine OFF
With the scan tool, observe the Stop Lamp Pedal Switch parameter and TCC/Cruise Brake Pedal Switch parameter in the Powertrain, Diesel, Data Display, Eng Data Display menu.
Press and release the brake pedal.
Does the Stop Lamp Pedal Switch parameter and TCC/Cruise Brake Pedal Switch parameter display change closely with each other?
Go to Diagnostic Aids
Go to Step 3

3
With the scan tool, observe the TCC/Cruise Brake Pedal Switch parameter.
Press and release the brake pedal.
Does the TCC/Cruise Brake Pedal Switch parameter display change with the brake pedal position?
Go to Step 6
Go to Step 4

4
Turn OFF the ignition.
Disconnect the stop lamp switch.
Turn ON the ignition, with the engine OFF.
Does the TCC/Cruise Brake Pedal Switch parameter display released?
Go to Step 5
Go to Step 12

5
Turn OFF the ignition.
Connect a 10-amp fused jumper between the ignition positive voltage circuit of the stop lamp switch and the TCC brake switch/cruise control release signal circuit of the stop lamp switch.
Turn ON the ignition, with the engine OFF.
Does the TCC/Cruise Brake Pedal Switch parameter display applied?
Go to Step 15
Go to Step 8

6
Turn OFF the ignition.
Disconnect the stop lamp switch.
Turn ON the ignition, with the engine off.
With the scan tool, observe the Stop Lamp Pedal Switch parameter.
Does the Stop Lamp Pedal Switch parameter display Released?
Go to Step 7
Go to Step 10

7
Turn OFF the ignition.
Connect a 20-amp fused jumper between the battery positive voltage circuit of the stop lamp switch and the stop lamp switch signal circuit.
Turn ON the ignition, with the engine OFF.
Does the Stop Lamp Pedal Switch parameter display Applied?
Go to Step 15
Go to Step 11

8
Test the ignition positive voltage circuit of the stop lamp switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 18
Go to Step 9

9
Test for an open or short to ground in the TCC brake switch/cruise control release signal circuit of the stop lamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 18
Go to Step 14

10
Test the stop lamp switch signal circuit 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 18
Go to Step 14

11
Test the battery positive voltage circuit of the stop lamp switch for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 18
Go to Step 13

12
Test the TCC brake switch/cruise control release signal circuit of the stop lamp switch 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 18
Go to Step 16

13
Test the stop lamp switch signal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 18
Go to Step 14

14
Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 18
Go to Step 16

15
Inspect for poor connections at the harness connector of the stop lamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 18
Go to Step 17

16
Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?
Go to Step 18
--

17
Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement .

Did you complete the replacement?
Go to Step 18
--

18
Use the scan tool in order to clear the DTCs .
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

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