37250-ZW9-901 Honda TACHOMETER ASSY. (Honda Code 6641302).

Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
2727-5
Starting System #1 Relay : Current Below Normal The Electronic Control Module (ECM) detects an open in the circuit for the starter relay.
The ECM detects a short to battery voltage in the circuit for the starter relay.
The ECM can only detect this condition when the output driver is not activated. The code is logged.
2727-6
Starting System #1 Relay : Current Above Normal The ECM detects a short in the circuit for the starter relay.
The ECM can only detect this condition when the output driver is activated.
2728-5
Starting System #2 Relay : Current Below Normal The Electronic Control Module (ECM) detects an open in the circuit for the starter relay.
The ECM detects a short to battery voltage in the circuit for the starter relay.
The ECM can only detect this condition when the output driver is not activated. The code is logged.
2728-6
Starting System #2 Relay : Current Above Normal The ECM detects a short in the circuit for the starter relay.
The ECM can only detect this condition when the output driver is activated. Use this procedure to troubleshoot the electrical system if a problem is suspected with the starting system.The ECM is provided with the ability to begin the engine cranking at any time after the ECM has received keyswitch power. The ECM receives the start command from the EMCP 3 via the global CAN data link. Once this request is received, the engine is placed into the "Prestart State" of the control for the engine state. If the engine is equipped with a prelubrication system, the engine will wait until the prelube cycle has been completed before initiating engine cranking.Configuration ParametersThe settings of the following configuration parameters control engine starting:
Starting System #1 Maximum Number of Crank Cycles
Starting System #1 Crank Cycle Rest Interval
Starting System #1 Crank Duration
Crank Terminate RPMConfiguration parameters for Starting System #2 are also available. Refer to Troubleshooting, "Configuration Parameters" for information that is related to these parameters.
Illustration 1 g06091129
Schematic for the engine starting system
There are also configuration parameters that are used to configure the ECM for the type and the location of the starting motors. The following types of starting motors can be used on this engine:
Air starting motor
Electric starting motor
Hydraulic starting motorThe wiring for each of these types of engine starting circuits is similar. Follow this procedure in order to troubleshoot the circuit diagnostics for any of these types of engine starting system.The ECM can control a secondary starting system that is installed on the engine opposite the primary starting system. Refer to Troubleshooting, "Configuration Parameters" for information that is related to the configuration parameters that are for the secondary starting system.ECM Activation of the Starting MotorsThe ECM utilizes two output drivers in order to crank the engine. Each output driver is provided with 24 VDC during engine cranking. The circuits for the output drivers utilize a return line to the ECM. This circuit includes crank relays that can be powered by an external power supply in order to override the ECM activation of the starting motors.Manual Overrides for the Engine Starting SystemThe engine can be manually cranked by using a manual crank switch that can be wired into the engine interface connector. The engine starting circuit incorporates four crank relays. When the relay coils are powered by 24 VDC, the starting motor magnetic switches are fused at the low current power distribution panel. The switch and the wiring for the circuit must be supplied by the customer.Caterpillar Electronic Technician (ET) can be used in order to override the output command that is provided by the engine state control. This override can be used to diagnose the circuit that is for the starting motor magnetic switches. View the "Starting System Relay Status" that is available in Cat ET in order to determine the status of the ECM outputs.
Illustration 2 g03321063
Location of the control box connectors for the engine starting system
(1) Right rail connector
(2) J2/P2 ECM connector
(3) Engine interface connector
(4) Left rail connector
(5) Manual crank relay (RH)
(6) Manual crank relay (LF)
Illustration 3 g01560016
Terminal locations at the P2 ECM connector for the engine starting system
(P2-32) Right starter enable −
(P2-44) Right starter enable +
(P2-59) Left starter enable +
(P2-60) Left starter enable −
Illustration 4 g01533453
Terminal locations at the keyswitch relay and the relay for the power mode circuit
(Terminal 1) Power to the starting motor magnetic switch
(Terminal 2) Power from the override switch that is used to override the ECM signal
(Terminal 3) Signal line or return line from the ECM
(Terminal 4) Power or return for the secondary circuit of the relay that is for the manual override
(Terminal 5) Return for the control circuit of the relay
Illustration 5 g01155187
Terminal locations at the connector for the starting motor magnetic switch
(Terminal 1) Relay signal circuit to the pump
(Terminal 2) Return
Table 2
Troubleshooting Test Steps Values Results
1. Inspect the Electrical Connectors and the Wiring
A. Turn the battery disconnect switch to the OFF position.
B. Thoroughly inspect the connectors that are associated with the starting system. Ensure that a circuit breaker has not tripped. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
D. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
E. Check the harness and the wiring for abrasion and for pinch points.
Connectors
Results: The connectors and wiring are OK.
Proceed to Test Step 2
Results: The connectors and/or wiring need repair.
Repair: Repair