G3500 A3 Engines Caterpillar

Illustration 1	g02290339
Location of the pressure switch for the jacket water cooling system (typical right rear engine view)

The coolant pressure switch is used to monitor the cooling system for a high coolant pressure. The pressure switch is located in the piping toward the right rear portion of cylinder block. The switch will trip when the pressure in the cooling system exceeds 462 ± 41 kPa (67 ± 6 psi). Tripping this switch effectively creates an open in the circuit for the switch.

Illustration 2	g02290353
Location of the pressure sensor for the jacket water cooling system (typical front engine view)

This engine is also equipped with a coolant pressure sensor. The coolant pressure sensor is used to monitor the cooling system for a low coolant pressure.

Note: If the outlet pressure of the coolant is greater than approximately 444 kPa (64 psi), the coolant pressure sensor may generate a 109-08 Engine Coolant Outlet Pressure Sensor abnormal frequency, pulse width, or period. This code may be generated although there is no malfunction in the electrical circuit. If this code is generated, verify the actual outlet pressure of the coolant with a pressure gauge. If the actual pressure is greater than approximately 444 kPa (64 psi), reduce the pressure. Reducing the pressure will prevent a false 109-08 Engine Coolant Outlet Pressure Sensor abnormal frequency, pulse width, or period from being activated. For information related to troubleshooting an electrical problem with the coolant pressure sensor, refer to Troubleshooting, "PWM Sensor" for details.

Probable Causes

• Excessive pressure in the jacket water cooling system

• Faulty pressure switch or switch circuit

Recommended Actions

Excessive Pressure in the Jacket Water Cooling System

Use a pressure gauge to confirm the pressure in the cooling system before the coolant enters the block. If a pressure of at least 462 ± 41 kPa (67 ± 6 psi) is measured in the cooling system, the high pressure may be caused by a restriction. Inspect the system for restrictions. Perform repairs, as needed.

If the pressure is less than 462 ± 41 kPa (67 ± 6 psi) and the E224 is active, there may be a problem with the switch or switch circuit.

Faulty Pressure Switch or Switch Circuit

The circuit for the pressure switch must remain closed in order to avoid a E224 High Jacket Water Inlet Pressure from occurring.

If an electrical problem is suspected with the switch or switch circuit, perform the following checks:

1. Check the circuit wiring for damage and corrosion. Refer to Troubleshooting, "Inspecting Electrical Connectors".

   If a problem with the wiring for the circuit is found, repair the wiring, as needed.

2. To check the condition of the switch, ensure that the engine is off and the pressure on the cooling system is minimal. For a switch that is in good repair, a resistance check between terminals B and C will show a continuous circuit.

3. Check the integrity of the engine harness and the switch input at the Electronic Control Module (ECM):

   1. Place the engine control switch in the Cooldown/Stop position.

   2. Disconnect the harness connector from the coolant pressure switch.

   3. Measure the voltage at the harness connector for the switch between terminals B and C.

      For a circuit that is in good repair, the pull-up voltage at the harness connector will be approximately 7.5 V.

      If the switch is in good repair and the voltage at the harness connector is OK, there is probably an intermittent electrical problem. Check the harness and connectors for a problem. Perform the necessary repairs.

      If there is a problem with the pull-up voltage at the harness connector, proceed to the next Test Step.

   4. Use a wire removal tool to remove the wiring for the switch circuit at the ECM connector. Refer to the appropriate Schematic for your engine for the proper ECM pin locations for the switch.

   5. Fabricate two jumper wires that are long enough create a test circuit at the ECM connector. Crimp a connector socket to one end of each of the jumper wires. Insert a jumper wire into each terminal location at the ECM connector for the switch.

   6. Measure the voltage between the jumper wires. The pull-up voltage at the ECM will be approximately 7.5 V

      If the voltage at the ECM is approximately 7.5 V and the voltage at the harness connector is incorrect, the problem is in the harness. Repair the harness, as necessary.

      If the voltage at the ECM is incorrect, there may be a problem with the ECM. Before you consider replacing the ECM, consult the Dealer Solutions Network (DSN) for assistance.