8M2000346 Mercruiser RETAINER

Table 1
Diagnostic Codes Table    
Code and Description    Conditions which Generate this Code    System Response    
264-8 Deceleration Throttle abnormal frequency, pulse width, or period     The Electronic Control Module (ECM) detects an open circuit and/or a short to the +Battery in the circuit for the decelerator position sensor.     The code is logged.
The ECM ignores the throttle input signals and the desired engine speed is set to 1000 rpm, unless the actual engine speed is below 1000 rpm. If the actual engine speed is below 1000 rpm, the desired engine speed is set to the current engine speed. The desired engine speed is set to low idle if the engine is not running.    The throttle switch provides the operator with the ability to select the desired engine speed. The throttle switch is a three-position momentary rocker switch. The three positions are Neutral, Rabbit, and Tortoise. The throttle switch can be used to select high idle or low idle. The throttle switch can also be used to adjust the maximum engine speed.High Idle - To increase engine speed to high idle, push the top of the switch (Rabbit) one time and release the switch.Low Idle - To decrease engine speed to low idle, push the bottom of the switch (Tortoise) one time and release the switch.Set Maximum Speed - Set the engine speed to high idle. Push on the decelerator pedal until the desired speed is reached. When this desired speed is reached, push on the top of the throttle control switch and hold for three seconds. This will electronically set the current engine speed as the maximum operating speed. The decelerator will function normally in order to reduce engine speeds below this maximum speed. In order to return to high idle as maximum speed, press the top part of the throttle control switch.The throttle switch is connected to the four throttle inputs of the ECM. Each position generates a specific on/off pattern on the throttle inputs. A diagnostic code is generated if a pattern that does not correspond with any of the switch positions is detected.Voltage at the inputs to the ECM for the throttle switch is 7.5 0.5 VDC when the throttle inputs are open. The voltage is less than 0.5 VDC when the throttle inputs are closed.Caterpillar Electronic Technician (ET) can be used to view the status of the inputs for the throttle switch.
Illustration 1 g01222823
Schematic for the throttle switchTest Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01415758
Location of ECM connectors
Thoroughly inspect the J1/P1 ECM connector. Refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01250533
Terminal locations at the P1 ECM connector (P1-22) Throttle input #1 (low) (P1-23) Throttle input #2 (low par) (P1-40) Throttle input #3 (high) (P1-41) Throttle input #4 (high par)
Illustration 4 g01250541
Terminal locations at the throttle switch (Terminal 1) Throttle input #1 (low) (Terminal 2) Return (Terminal 3) Throttle input #4 (high par) (Terminal 4) Throttle input #2 (low par) (Terminal 5) Return (Terminal 6) Throttle input #3 (high)
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and at the connector for the throttle switch.
Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for corrosion, for abrasion, and for pinch points from the throttle switch to the ECM.Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem in the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Check the Status of the Throttle Inputs
Connect Cat ET to the service tool connector.
Turn the keyswitch to the ON position.
Observe the status of the throttle inputs on Cat ET while you operate the throttle switch in each position.
Table 2
Throttle Input    Neutral    High "Rabbit"    Low "Tortoise"    
"#1 (Low)"     Off     Off     On    
"#2 (Low Par)"     On     Off     On    
"#3 (High)"     Off     On     Off    
"#4 (High Par)"     On     On     Off    Expected Result:The status of the throttle switch corresponds with table 2 above.Results:
OK - The status of the throttle switch is correct.Repair: The throttle switch is functioning properly at this time. There may be an intermittent electrical problem in the wiring harness or in a connector. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for troubleshooting information.STOP
Not OK - One or more of the inputs is incorrect. There is a problem in the circuit for the throttle switch. Proceed to Test Step 3.Test Step 3. Check the Harness between the Throttle Switch and the ECM
Turn the keyswitch to the OFF position.
Fabricate two jumper wires that are long enough to create a short circuit across the connector for the throttle switch. Crimp spade terminals to each end of the jumper wires.
Disconnect the wires for the suspect throttle inputs from the throttle switch. Refer to Table 4.
Table 3
Throttle Input    Neutral    High "Rabbit"    Low "To