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3512C Engine for Caterpillar Built Machines Caterpillar


Start/Run/Stop Switch

Usage:

SPF343C RTX
System Operation Description:

Use this procedure in order to troubleshoot the starting system or use this procedure if the diagnostic code in Table 1 is active or easily repeated.

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Table 1
Diagnostic Codes Table    
Description     Conditions which Generate this Code     System Response    
336-2 Engine Control Switch erratic, intermittent, or incorrect     The two inputs from the start/run/stop switch are in the opposite state.     The code is logged.    

The ADEM box receives a signal from the main junction box that goes to the start/run/stop inputs on the Electronic Control Module (ECM). The signal goes to the terminal strip in the ADEM box. Two separate wires from the terminal strip are wired to two inputs for the start/run/stop switch on the ECM. The signals allow the ECM to determine the status of the "Start" button and the "Kill" button on the control panel.

When both of the start/run/stop inputs are connected to the digital return, the ECM determines that the "Start" button is active. The ECM will begin the engine start sequence. When both of the signals are floating, the ECM determines that the "Kill" button is active. If the "Kill" button is active, the ECM shuts down the engine.

If the two signals are at a different potential, the ECM will determine that one of the signals is incorrect. A diagnostic code will be logged and a diagnostic code will remain active. The ECM will not begin the starting sequence. If the engine is running and the ECM detects a different potential between the two signals, the ECM will continue to enable injection.

The input signals to the ECM are in series with the digital return through a set of normally open contacts of the "Start Deck Engine Relay (SDER)" and through a set of normally closed contacts of the "Fuel Cutoff Relay (FCR)". When the "Start" button on the control panel is activated, the master "DCU" energizes the "Start Deck Engine Relay (SDER)". The normally open contacts of the "Start Deck Engine Relay (SDER)" will close. The ECM will begin the engine start sequence, when the input signals to the ECM are connected to the digital return.

When the "Start Deck Engine Relay (SDER)" is de-energized or the "Fuel Cutoff Relay (FCR)" is energized, the start/run/stop inputs to the ECM will float. The ECM will initiate the shutdown sequence.

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Illustration 1g01286693

Typical example

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Illustration 2g01286694

P1 ECM connector

(P1-5) Digital return

(P1-23) Start/run/stop input 1

(P1-28) Start/run/stop input 2

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Illustration 3g01285750

Location of ECM connectors

Test Step 1. Check for an Active Diagnostic Code

  1. Turn the "main disconnect switch (MDS)" to the ON position.

  1. Start Caterpillar Electronic Technician (ET).

  1. Check for an active 336-2 diagnostic code.

Expected Result:

The 336-2 diagnostic code is not active.

Results:

  • OK - The 336-2 diagnostic code is not active. Proceed to Test Step 2.

  • Not OK - The 336-2 diagnostic code is active.

    Repair: If the diagnostic code 336-2 is active, the start/run/stop inputs between the ECM and the terminal 103 in the ADEM box are in opposite states. Check the wires for an open or for a short circuit.

    1. Check the wires for an open circuit.

      1. Disconnect the J1/P1 ECM connector.

      1. Measure the resistance between P1-21 at ECM connector P1 and terminal 103 on the terminal strip.

      1. Measure the resistance between P1-22 at ECM connector P1 and terminal 103 on the terminal strip.

      1. If the resistance measurement indicates an open circuit, repair the wires and/or connectors between the terminal strip and the ECM.

    1. Check the wires for a short circuit.

      1. Disconnect the J1/P1 ECM connector and the J2/P2 ECM connector.

      1. Disconnect the wire F716-BK and wire F717-BK from terminal 103 in the ADEM box.

      1. Measure the resistance between P1-21 and every terminal on ECM connector P1 and ECM connector P2.

      1. Measure the resistance between P1-21 and engine ground.

      1. Measure the resistance between P1-22 and every terminal on ECM connector P1 and ECM connector P2.

      1. Measure the resistance between P1-22 and engine ground.

      1. If the resistance measurement indicates a short circuit, repair the wires and/or connectors between the terminal strip and the ECM.

    STOP

Test Step 2. Check the Status while the Start/Run/Stop Switch is Active

  1. Observe the status of the start/run/stop switch on Cat ET.

  1. Turn the start/run/stop switch to the START/RUN position.

Expected Result:

The status for the start/run/stop switch reads "START".

Results:

  • OK - The status for the start/run/stop switch reads "START". Proceed to Test Step 3.

  • Not OK - The status for the start/run/stop switch does not display "START". Proceed to Test Step 4.

Test Step 3. Check the Status while the Start/Run/Stop Switch is Not Active

  1. Turn the start/run/stop switch to the STOP position.

  1. Observe the status of the start/run/stop switch on Cat ET.

Expected Result:

The status for the start/run/stop switch reads "STOP".

Results:

  • OK - The status for the start/run/stop switch reads "STOP".

    Repair: The start/run/stop switch is functioning correctly. There may be an intermittent problem. If the problem is intermittent, refer to Troubleshooting, "Inspecting Electrical Connectors".

    STOP

  • Not OK - The status for the start/run/stop switch does not read "STOP". Proceed to Test Step 6.

Test Step 4. Check the Signal for the Start/Run/Stop Switch in the ADEM Box for an Open Circuit

  1. Turn the "MDS" to the OFF position.

  1. Disconnect the wire from the main junction box that is on terminal 101 in the ADEM box.

  1. Disconnect the wire from the main junction box that is on terminal 103 in the ADEM box.

  1. Turn the "MDS" to the ON position.

  1. Turn the start/run/stop switch to the START/RUN position.

  1. Measure the resistance between the wires that were disconnected from terminal 101 and from terminal 103.

  1. Turn the start/run/stop switch to the STOP position.

  1. Turn the "MDS" to the OFF position.

  1. Replace all wires to the original configuration.

Expected Result:

The resistance measurement indicates a short circuit.

Results:

  • OK - The resistance measurement indicates a short circuit.

    Repair: Check the wire 998-BK for an open circuit between terminal 101 in the ADEM box and the ECM. Check for an open circuit in the wires between terminal 103 in the ADEM box and ECM terminals P1-21 and P1-22.

    STOP

  • Not OK - The resistance measurement indicates an open circuit. Proceed to Test Step 5.

Test Step 5. Check the Signal for the Start/Run/Stop Switch at the Main Junction Box for an Open Circuit

  1. Disconnect the wire from TB-36 in the main junction box that goes to the ADEM box.

  1. Disconnect the wire from TB-15 in the main junction box that goes to the ADEM box.

  1. Turn the "MDS" to the ON position.

  1. Turn the start/run/stop switch to the START/RUN position.

  1. Measure the resistance between TB-36 and TB-15 in the main junction box.

  1. Turn the start/run/stop switch to the STOP position.

  1. Turn the "MDS" to the OFF position.

  1. Replace all wires to the original configuration.

Expected Result:

The resistance measurement indicates a short circuit.

Results:

  • OK - The resistance measurement indicates a short circuit.

    Repair: One of the wires between the main junction box and the ADEM box has an open circuit. Repair the wire.

    STOP

  • Not OK - The resistance measurement indicates an open circuit.

    Repair: Verify that the "Fuel Cutoff Relay (FCR)" is not energized. The contacts of the "Start Deck Engine Relay (SDER)" or the "SDER" is not working properly. Repair the wiring to the "SDER" or repair the "SDER".

    STOP

Test Step 6. Check the Signal for the Start/Run/Stop Switch in the ADEM Box for a Short Circuit

  1. Turn the "MDS" to the OFF position.

  1. Disconnect the wire F716-BK and wire F717-BK from terminal 103 in the ADEM box.

  1. Turn the "MDS" to the ON position.

  1. Observe the status of the start/run/stop switch on Cat ET.

  1. Turn the "MDS" to the OFF position.

  1. Replace all wires to the original configuration.

Expected Result:

The status for the start/run/stop switch reads "STOP".

Results:

  • OK - The status for the start/run/stop switch reads "STOP". Proceed to Test Step 7.

  • Not OK - The status for the start/run/stop switch reads "START".

    Repair: Check the wire F716-BK for a short circuit to engine ground or for a short to a wire in one of the ECM connectors. Check the wire F717-BK for a short circuit to engine ground or for a short to a wire in one of the ECM connectors. Repair the wire.

    STOP

Test Step 7. Check the Signal for the Start/Run/Stop Switch at the Main Junction Box for a Short Circuit

  1. Turn the "MDS" to the OFF position.

  1. Disconnect the wire from TB-36 in the main junction box that goes to the ADEM box.

  1. Turn the "MDS" to the ON position.

  1. Observe the status of the start/run/stop switch on Cat ET.

  1. Turn the "MDS" to the OFF position.

  1. Replace all wires to the original configuration.

Expected Result:

The status for the start/run/stop switch reads "STOP".

Results:

  • OK - The status for the start/run/stop switch reads "STOP".

    Repair: The wiring between the main junction box and the ECM junction box is OK. Verify that the "Fuel Cutoff Relay (FCR)" is not energized. The contacts of the "Start Deck Engine Relay (SDER)" or the "SDER" is not working properly. Repair the wiring to the "SDER" or repair the "SDER".

    STOP

  • Not OK - The status for the start/run/stop switch reads "START".

    Repair: There is short in the wire between terminal TB-36 in the main junction box and terminal 103 in the ECM junction box. Repair the wire.

    STOP

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