HEAT EXCHANGER 2H9868 - Caterpillar

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(1) Primary engine speed/timing sensor (2) Secondary engine speed/timing sensor
Thoroughly inspect the connectors for the engine speed/timing sensors (1) and (2). Refer to Troubleshooting, "Electrical Connectors - Inspect".
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Location of the P2 ECM connector (typical left side engine view)
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P2 terminal locations for the engine speed sensors (P2-48) Primary engine speed/timing sensor + (P2-49) Primary engine speed/timing sensor - (P2-58) Secondary engine speed/timing sensor + (P2-59) Secondary engine speed/timing sensor -
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the engine speed/timing sensors.
Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points from each sensor back to the ECM.Expected Result:All of the connectors, pins and sockets are completely coupled and/or inserted and 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 4.
Not OK - The connectors and/or wiring are not OK.Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. 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 4. Measure the Sensor Resistance at the ECM Connector
Disconnect the J2/P2 ECM connector.
Use the following procedure to measure the circuit resistance for the primary engine speed/timing sensor:
Measure the resistance between P2-48 (primary engine speed/timing +) and P2-49 (primary engine speed/timing −).Note: Check for an intermittent problem (open or short) by moving the harness while you measure the resistance. Pull the wires that are directly behind the sensors and shake the wires that are directly behind the sensors.Resistance ... 75 to 230 Ohms
Use the following procedure to measure the circuit resistance for the secondary engine speed/timing sensor:
Measure the resistance between P2-58 (secondary engine speed/timing +) and P2-59 (secondary engine speed/timing −).Note: Check for an intermittent problem (open or short) by moving the harness while you measure the resistance. Pull the wires that are directly behind the sensors and shake the wires that are directly behind the sensors.Resistance ... 600 to 1800 OhmsExpected Result:The resistance measurement is within the specifications.Results:
OK - The resistance measurement is within the specifications.Repair: The sensors and the harness are OK.
Temporarily connect a test ECM.
If the problem is resolved with the test ECM, reconnect the suspect ECM.
If the problem returns with the suspect ECM, replace the ECM.STOP
Not OK - The resistance is not within the acceptable range when the circuit resistance is measured through the engine harness. Proceed to Test Step 5.Test Step 5. Measure the Sensor Resistance at the Connector for the Sensor
Disconnect the suspect sensor from the engine harness.
Thoroughly inspect the connector for the suspect engine speed/timing sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Measure the resistance between terminal 1 and terminal 2 of the sensor connector.Expected Result:For the primary engine speed/timing