3512B Generator Set Engine Caterpillar

Engine Control Switch - Test

Usage:

System Operation Description:

Use this procedure in order to troubleshoot the engine control switch (ECS) 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
Code and Description	Conditions which Generate this Code	System Response
336-2 Engine Control Switch : Erratic, Intermittent, or Incorrect	The two inputs from the engine control switch are in the opposite state.	The code is logged.

The ECS can operate in four modes: OFF, START, STOP and REMOTE.

The primary electronic control module (ECM) receives three signals that allow the ECM to determine the mode of operation. The input signals on P1-21 and P1-22 tell the ECM to either start or stop the engine. The input signals on P1-21 and P1-22 must be at the same potential or a diagnostic code will be generated. The third input signal on P1-68 tells the ECM if the ECS is in the START position. If the input signal on P1-68 is low, the ECM knows that the ECS is in the START position. If the input signal on P1-68 is not low, the ECM knows that the ECS is not in the START position.

When the ECS is in the REMOTE position, inputs from the customer control the operation of the engine. The following list contains some of the inputs from the customer connector and the inputs function.

C remote start 2
D remote start 1
E remote stop 1
F remote stop 2
S "ECS (remote/auto)"
c keyswitch

When the ECS is in the REMOTE position, the "Remote Start" relay and the "Remote Stop" relay are energized. When the remote start inputs C and D from the customer connector go low, the following relays energize: "Run 1" relay, "Run 2" relay, "Reset 1" relay and "Reset 2" relay. The start/run/stop inputs P1-21 and P1-22 will be pulled low. The ECM will begin the start cycle. The "Stop 1" relay and the "Stop 2" relay latch the "Run 1" relay and the "Run 2" relay in the energized state.

When the customer's remote stop inputs F and E go low, the following relays energize: "Stop 1" relay and "Stop 2" relay. The "Run 1" relay and the "Run 2" relay will de-energize. The start/run/stop inputs P1-21 and P1-22 will float high. The injection signals to the injectors will stop and the engine will shut down. The "Run 1" relay and the "Run 2" relay latch the "Stop 1" relay and the "Stop 2" relay in the energized state.

When the ECS is in the START position, the "ECS in Start" relay energizes. The "ECS in Start" relay sends a signal to the customer connector that allows the customer to determine the position of the ECS.

When the ECS is in the START position, the following relays energize: "Run 1" relay, "Run 2" relay, "Reset 1" relay, "Reset 2" relay and "ECS in Start" relay. The "ECS in Start" relay sends a signal to the customer connector that tells the customer that the ECS is in the START position. The start/run/stop inputs P1-21 and P1-22 will be pulled low. The ECM will begin the start cycle. The "Stop 1" relay and the "Stop 2" relay latch the "Run 1" relay and the "Run 2" relay in the energized state.

When the ECS is in the STOP position and the OFF position, the following relays energize: "Stop 1" relay and "Stop 2" relay. The "Run 1" relay and the "Run 2" relay will de-energize. The start/run/stop inputs P1-21 and P1-22 will float high. The injection signals to the injectors will stop and the engine will shut down. The "Run 1" relay and the "Run 2" relay latch the "Stop 1" relay and the "Stop 2" relay in the energized state.

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Illustration 1	g01625345
Typical example

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Illustration 2	g01324452
P1 Primary ECM connector (P1-21) "Start/Run/Stop 1" (P1-22) "Start/Run/Stop 2"

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Illustration 3	g01324924
P2 Primary ECM connector (P2-54) "Digital return" (P2-55) "Digital return"

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Illustration 4	g01622856
Connector locations (1) A-C1/E-C2/E-C1 Right hand cross over harness (2) A-C2/J-C2/J-C1 Right hand cross over harness (3) A-C90/P-C1 Connectors for the power distribution panel (4) A-C91/P-C2 Connectors for the power distribution panel (5) A-C60 Connector for the prelube motor (6) A-C92/F-C1/F-C2/G-C6 Connectors for a RH Control panel (7) C-C22 Primary ECM connector P2 (8) C-C15 Primary ECM connector P1 (9) C-C28 Secondary ECM connector P2 (10) C-C29 Secondary ECM connector P1 (11) C-C47 Connector for the power relay panel (12) C-C17/F-C1/F-C2/G-C6 Connectors for a LH Control panel (13) C-C18/(TB-C1 customer or L-C1/L-C2 EMCP 3) connectors (14) C-C2/J-C1/J-C2 Left hand cross over harness (15) C-C1/E-C1/E-C2 Left hand cross over harness

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Illustration 5	g01324537
Terminal locations for the A-C1/E-C2/E-C1 Right hand cross over harness and the C-C1/E-C1/E-C2 Left hand cross over harness (Terminal i) "Start/Run/Stop 1" (Terminal j) "Start/Run/Stop 2" (Terminal AL) "Digital return" (Terminal AK) "Digital return"

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Illustration 6	g01324917
Terminal locations for the following connectors A-C92/F-C1/F-C2/G-C6 Connectors for a RH Control panel and C-C17/F-C1/F-C2/G-C6 Connectors for a LH Control panel (Terminal 19) "Start/Run/Stop 1" (Terminal 20) "Start/Run/Stop 2" (Terminal 23) Digital return (Terminal 45) Digital return

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Illustration 7	g01324914
Terminal locations for the C-C18/(TB-C1 customer or L-C1/L-C2 EMCP 3) connectors (Terminal C) "Remote start 2" (Terminal D) "Remote start 1" (Terminal E) "Remote stop 1" (Terminal F) "Remote stop 2" (Terminal S) "ECS in remote" (Terminal c) "Keyswitch"

Test Step 1. Inspect the Electrical Connectors and the Wiring

Turn the circuit breaker for the battery to the OFF position.
Turn the ECS to the OFF position.
Thoroughly inspect the primary ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Check the allen head screw on each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion or of pinch points.

Results:

OK - The connectors and wiring are OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring need repair.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

STOP

Test Step 2. Check the Status of the ECS in the STOP Position

Turn the circuit breaker for the battery to the ON position.
Connect the Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the ECS to the STOP position.
Observe the status for the ECS on Cat ET.

Expected Result:

The status for the ECS is "STOP".

Results:

OK - The ECS is functioning correctly. Proceed to Test Step 3.
Not OK - The status for the ECS is not "STOP". Proceed to Test Step 5.

Test Step 3. Check the Status of the ECS in the START Position

Turn the ECS to the START position.
Observe the status for the ECS on Cat ET.

Expected Result:

The status for the ECS is "RUN".

Results:

OK - The ECS is functioning correctly. Proceed to Test Step 4.
Not OK - The status of the ECS is not "RUN". Proceed to Test Step 5.

Test Step 4. Check the Status of the ECS in the REMOTE Position

Turn the ECS to the REMOTE position.
Observe the status for the ECS on Cat ET.

Expected Result:

The status for the ECS is "AUTO".

Results:

OK - The ECS is working correctly.
Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

STOP
ECS Not OK - The status for the ECS is not "AUTO". Proceed to Test Step 6.

Test Step 5. Install a Wire Jumper at the ECM in order to Simulate a START/STOP Function

Turn the ECS to the OFF position.
Disconnect the primary ECM connector P1.
Remove wire F716 from P1-21. Install a wire jumper into the socket P1-21.
Remove wire F717 from P1-22. Install a wire jumper into the socket P1-22.
Reconnect the primary ECM connector P1.
Fabricate a wire jumper.
Install the wire jumper between the wire jumpers in P1-21 and P1-22 and engine ground.
Turn the ECS to the STOP position.
Observe the status for the ECS on Cat ET.
Remove the wire jumper between the wire jumpers in P1-21 and P1-22 and engine ground.
Observe the status for the ECS on Cat ET.
Turn the ECS to the OFF position. Remove the wire jumpers and replace all wires. Reconnect the primary ECM connector P1.

Expected Result:

The status for the ECS displays "RUN" while the wire jumper is installed. The status for the ECS displays "STOP" when the wire jumper is removed.

Results:

OK - The status for the ECS displays the proper states. The problem is not with the ECM. Troubleshoot the wire F716 and the wire F717. In order to troubleshoot the wire F716, proceed to Test Step 7.
Not OK - The status for the ECS does not display the correct state.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

STOP

Test Step 6. Install a Wire Jumper at the ECM in order to Simulate an AUTO Condition

Turn the ECS to the OFF position.
Disconnect the primary ECM connector P1.
Remove wire F721 from P1-68. Install a wire jumper into the socket P1-68.
Reconnect the primary ECM connector P1.
Fabricate a wire jumper.
Install the wire jumper between the wire jumper in P1-68 and engine ground.
Turn the ECS to the STOP position.
Observe the status for the ECS on Cat ET.
Remove the wire jumper between the wire jumper in P1-68 and engine ground.
Observe the status for the ECS on Cat ET.
Turn the ECS to the OFF position. Remove the wire jumpers and replace all wires. Reconnect the primary ECM connector P1.

Expected Result:

The status for the ECS displays "AUTO" while the wire jumper is installed. The status for the ECS displays "OFF" when the wire jumper is removed.

Results:

OK - The status for the ECS displays the proper states. The problem is not with the ECM.
Repair: Perform the following steps.
1. Check continuity of wire F721 between the ECS and the P1-68 primary ECM connector.
2. Check continuity of wire G721 between the ECS and terminal S of the customer connector.
Repair any opens in the wiring. Repair any shorts in the wiring.

STOP
Not OK - The status for the ECS does not display the correct state.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".

STOP

Test Step 7. Check for Voltage on Wire F716 at the Normally Closed Contacts of the "Stop 1" Relay

Turn the ECS to the OFF position.
Remove wire F716 from terminal 22 of the "Stop 1" relay.
Turn the ECS to the STOP position.
Measure the voltage between wire F716 and engine ground.
Turn the ECS to the OFF position.
Replace all wiring to the original configuration.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Proceed to Test Step 8.
Not OK - The voltage is not 6.5 ± 0.5 VDC.
Repair: Repair the wire F716 between the normally closed contacts on the "Stop 1" relay and the ECM. Refer to Illustration 1 for a schematic of the connections between the control panel and the ECM.

STOP

Test Step 8. Check for Voltage at the Normally Closed Contacts of the "Stop 1" Relay

Remove wire DM775 from terminal 21 of the "Stop 1" relay.
Turn the ECS to the START position.
Measure the voltage between terminal 21 of the "Stop 1" relay and engine ground.
Turn the ECS that is on the control panel to the OFF position.
Replace all wiring to the original configuration.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Proceed to Test Step 9.
Not OK - The voltage is not 6.5 ± 0.5 VDC. The "Stop 1" relay's normally closed contacts are faulty or the "Stop 1" relay is energized.
Repair: Check the voltage across the coil of the "Stop 1" relay. If voltage is present across the coil of the "Stop 1" relay, ensure that the ECS is not in the STOP position.
If no voltage is measured across the coil of the "Stop 1" relay, the normally closed contacts between wire F716 and wire DM775 are faulty. Replace the "Stop 1" relay and check for diagnostic codes.

STOP

Test Step 9. Check for Voltage on Wire DM775

Remove wire DM775 from terminal 21 of the "Run 1" relay.
Remove wire PR775 from terminal 11 of the "Remote Start" relay.
Turn the ECS to the START position.
Measure the voltage between wire DM775 and engine ground at the "Run 1" relay.
Measure the voltage between wire PR775 and engine ground at the "Remote Start" relay.
Turn the ECS that is on the control panel to the OFF position.
Leave wire DM775 disconnected from terminal 21 of the "Run 1" relay. Reconnect wire PR775 to terminal 11 of the "Remote Start" relay.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Proceed to Test Step 10.
Not OK - The voltage is not 6.5 ± 0.5 VDC.
Repair: There is a problem with the wire DM775 between the "Stop 1" relay and the "Run 1" relay. Repair the wire DM775.
There is a problem with the wire DM775 between the "Stop 1" relay and the "Remote Start" relay. Check for voltage on wire DM775 at diode D2. If voltage is present at diode D2, the problem is in wire PR775. If voltage is not present at diode D2, the problem is in wire DM775.

STOP

Test Step 10. Check for Voltage at the Normally Closed Contacts of the "Remote Start" Relay

Remove wire LR775 from terminal 12 of the "Remote Start" relay.
Turn the ECS to the START position.
Measure the voltage between terminal 12 of the "Remote Start" relay and engine ground.
Turn the ECS that is on the control panel to the OFF position.
Reconnect wire LR775 to terminal 12 of the "Remote Start" relay.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Proceed to Test Step 11.
Not OK - The voltage is not 6.5 ± 0.5 VDC. The "Remote Start" relay is energized or there is a problem with the normally closed contacts of the "Remote Start" relay between wire LR775 and wire PR775.
Repair: Check the voltage across the coil of the "Remote Start" relay. Voltage should not be present across the coil. If voltage is present, verify that the ECS is not in the REMOTE position. Check for a short in wire R791.
If voltage is not present across the coil of the "Remote Start" relay, replace the "Remote Start" relay.

STOP

Test Step 11. Check for Voltage on Wire LR775 at Terminal 9 of the ECS

Remove wire LR775 from terminal 9 of the ECS.
Turn the ECS to the START position.
Measure the voltage between wire LR775 and engine ground.
Turn the ECS that is on the control panel to the OFF position.
Reconnect wire LR775 to terminal 9 of the ECS. Reconnect wire DM775 to terminal 21 of the "Run 1" relay.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Wire F716 is OK. Proceed to Test Step 12 in order to check wire F717.
Not OK - The voltage is not 6.5 ± 0.5 VDC.
Repair: There is a problem with the wire LR775 between terminal 9 of the ECS and the "Remote Start" relay. Repair the wire LR775.

STOP

Test Step 12. Check for Voltage on Wire F717 at the Normally Closed Contacts of the "Stop 2" Relay

Turn the ECS to the OFF position.
Remove wire F717 from terminal 22 of the "Stop 2" relay.
Turn the ECS to the STOP position.
Measure the voltage between wire F717 and engine ground.
Turn the ECS that is on the control panel to the OFF position.
Replace all wiring to the original configuration.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Proceed to Test Step 13.
Not OK - The voltage is not 6.5 ± 0.5 VDC.
Repair: Repair the wire F717 between the normally closed contacts on the "Stop 2" relay and the ECM. Refer to Illustration 1 for a schematic of the connections between the control panel and the ECM.

STOP

Test Step 13. Check for Voltage at the Normally Closed Contacts of the "Stop 2" Relay

Remove wire DM776 from terminal 21 of the "Stop 2" relay.
Turn the ECS to the START position.
Measure the voltage between terminal 21 of the "Stop 2" relay and engine ground.
Turn the ECS that is on the control panel to the OFF position.
Replace all wiring to the original configuration.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Proceed to Test Step 14.
Not OK - The voltage is not 6.5 ± 0.5 VDC. There is a problem with the normally closed contacts of the "Stop 2" relay or the "Stop 2" relay is energized.
Repair: Check the voltage across the coil of the "Stop 2" relay. If voltage is present across the coil of the "Stop 2" relay, ensure that the ECS is not in the STOP position.
If no voltage is measured across the coil of the "Stop 2" relay, there is a problem with the normally closed contacts between wire F717 and wire DM776. Replace the "Stop 2" relay and check for diagnostic codes.

STOP

Test Step 14. Check for Voltage on Wire DM776

Remove wire DM776 from terminal 21 of the "Run 2" relay.
Remove wire PR776 from terminal 21 of the "Remote Start" relay.
Turn the ECS to the START position.
Measure the voltage between wire DM776 and engine ground at the Run 2 relay.
Measure the voltage between wire PR776 and engine ground at the Remote Start relay.
Turn the ECS to the OFF position.
Leave wire DM776 disconnected from terminal 21 of the "Run 2" relay. Reconnect wire PR776 to terminal 21 of the "Remote Start" relay.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Proceed to Test Step 15.
Not OK - The voltage is not 6.5 ± 0.5 VDC.
Repair: There is a problem with the wire DM776 between the "Stop 2" relay and the "Run 2" relay. Repair the wire DM776.
There is a problem with the wire DM776 between the "Stop 2" relay and the "Remote Start" relay. Check for voltage on wire DM776 at diode D5. If voltage is present at diode D5, the problem is in wire PR776. If voltage is not present at diode D5, the problem is in wire DM776.

STOP

Test Step 15. Check for Voltage at the Normally Closed Contacts of the "Remote Start" Relay

Remove wire LR775 from terminal 22 of the "Remote Start" relay.
Turn the ECS to the START position.
Measure the voltage between terminal 22 of the "Remote Start" relay and engine ground.
Turn the ECS to the OFF position.
Reconnect wire LR775 to terminal 22 of the "Remote Start" relay.

Expected Result:

The voltage is 6.5 ± 0.5 VDC.

Results:

OK - The voltage is 6.5 ± 0.5 VDC. Wire F717 is OK.
Repair: Check the ECS for proper operation. Check continuity between terminal 6 and terminal 9 of the ECS. Check continuity with the ECS in the START and STOP positions.
Refer to Illustration 1 for a schematic of the connections between the control panel and the ECM.

STOP
Not OK - The voltage is not 6.5 ± 0.5 VDC. The "Remote Start" relay is energized or there is a problem with the normally closed contacts of the "Remote Start" relay between wire LR775 and wire PR776.
Repair: Check the voltage across the coil of the "Remote Start" relay. Voltage should not be present across the coil. If voltage is present, verify that the ECS is not in the REMOTE position. Check for a short in wire R791.
If voltage is not present across the coil of the "Remote Start" relay, replace the "Remote Start" relay.

STOP