G3500 A3 Engines Caterpillar

Use this procedure to troubleshoot the following diagnostic codes:

• 145-3 12 Volt DC Power Supply voltage above normal

• 145-4 12 Volt DC Power Supply voltage below normal

• 320-3 Speed/Timing Sensor short to +batt

• 320-8 Engine Speed/Timing signal abnormal

Illustration 1	g00893441
Speed/Timing sensor and timing ring

The speed/timing sensor provides information about engine speed and the position of the crankshaft to the Electronic Control Module (ECM). The sensor is powered by the sensor supply (12 VDC) from the ECM. A magnetic pickup is located in the plastic sliphead of the sensor. The timing ring is mounted on the rear of the left camshaft. As the teeth of the ring rotate past the sliphead of the sensor, the sensor generates a signal that matches the pattern of the teeth.

The timing ring has a special tooth pattern that indicates the position of the camshaft and the direction of rotation. The timing ring has 24 slots in the outer diameter. Twenty−one of the slots are narrow. Three of the slots are about 2.5 times wider than the rest of the slots. When the engine rotates in the normal direction, the slots pass the speed/timing sensor in the following order:

• 1 wide slot

• 3 narrow slots

• 2 wide slots

• 18 narrow slots

The number one cylinder is at the top center position when the leading edge of the third narrow slot passes the center of the sliphead. All 24 teeth pass the sliphead during one revolution of the camshaft or two revolutions of the crankshaft.

With the information from the engine speed/timing sensor, the ECM is able to calculate the positions of the pistons in the cylinders. The ECM determines the desired ignition timing according to the engine speed and load. If detonation is detected in any of the cylinders, the ECM retards the timing of the affected cylinders. The ECM sends voltage pulses to the ignition transformers for firing the spark plugs according to the desired timing.

During engine operation, the ECM will shut down the engine if the ECM detects a problem with the signal from the speed/timing sensor. The ECM will activate the corresponding diagnostic code.

If there is a problem with the engine speed/timing sensor's signal during start-up but no corresponding diagnostic code is active, the ECM will not initiate the ignition. The engine will not start. The corresponding diagnostic code is not activated.

The most likely causes of the diagnostic code are a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with the engine speed/timing sensor. The least likely cause is a problem with the ECM.

The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.

Illustration 2	g01251119
Schematic of the circuit for the speed/timing sensor

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Set the engine control to the OFF/RESET position.
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   Illustration 3	g01392725
   Location of the components for the speed/timing sensor (1) J1/P1 ECM connectors (2) Speed/timing sensor

   Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".

2. Thoroughly inspect connectors (1) and the connector for sensor (2).

   1. Check the allen head screw for each of the ECM connectors for the proper torque.
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      Illustration 4	g01392729
      Terminal locations at the P1 ECM connector for the speed/timing sensor (P1-33) Speed/timing sensor (P1-43) +Battery (P1-51) Return

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the speed/timing sensor.
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      Illustration 5	g01256587
      Speed/timing sensor

   3. Check the harness and wiring for abrasion and for pinch points from the speed/timing sensor to the ECM.

Expected Result:

All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - The components are not in good condition and/or at least one connection is improper.

  Repair: Perform the necessary repairs and/or replace parts, if necessary.

  STOP

Test Step 2. Check the Sensor

1. Set the engine control to the OFF/RESET position.

2. Remove the speed/timing sensor.
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   Illustration 6	g01055553
   Plastic sliphead for the speed/timing sensor

3. Inspect the condition of the plastic sliphead. Look for signs of wear and for contaminants. Clean any debris from the plastic sliphead.

4. Check the tension of the plastic sliphead. Gently extend the plastic sliphead for a minimum of 4 mm (0.16 inch). Then push back the plastic sliphead.

Expected Result:

The sensor is in good condition. At least 22 N (5 lb) of force is required to push in the plastic sliphead from the extended position.

Results:

• OK - The sensor is not damaged. The tension of the plastic sliphead is correct.

  Repair: Install the sensor according to the following procedure:

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  NOTICE
  The plastic sliphead must be fully extended when the speed/timing sensor is installed so that the sensor maintains the correct clearance with the timing ring. If the correct clearance is not maintained, the signal from the sensor will not be generated. Do not install the sensor's plastic sliphead between the teeth of the timing ring. Damage to the plasic sliphead will result. Before installing the sensor, ensure that a tooth of the ring is visible in the mounting hole for the sensor.

  1. Ensure that a tooth on the timing ring is visible in the mounting hole for the sensor.

  2. Fully extend the sliphead.

     Note: The plastic sliphead is designed to contact the tooth of the timing ring during installation. As the timing ring begins to turn, the radial runout of the timing ring will push the plastic sliphead into the sensor body slightly. This provides the plastic sliphead's air gap with a self-adjusting function. The maximum allowable clearance between the sliphead and a tooth on the timing ring is 0.5 mm (0.02 inch).

  3. Coat the threads of the sensor with 4C-5597 Anti-Seize Compound.

  4. Install the sensor. Tighten the sensor to 40 ± 5 N·m (30 ± 4 lb ft).

  Proceed to Test Step 3.

• Not OK - The plastic sliphead is damaged and/or the tension of the sliphead is insufficient.

  Repair: Install a new sensor.

  If the condition is not resolved, proceed to Test Step 3.

Test Step 3. Check for Active Diagnostic Codes for the 12 Volt Sensor Supply

1. Establish communication between Caterpillar Electronic Technician (ET) and the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

2. Set the engine control to the COOLDOWN/STOP position.

3. Use the "Active Diagnostic" screen on Cat ET. Look for the following codes:

   • 145-3 12 Volt DC Power Supply voltage above normal

   • 145-4 12 Volt DC Power Supply voltage below normal

Expected Result:

None of the above codes are active.

Results:

• No active codes - None of the above codes are active. However, at least one of the codes is logged.

  Repair: Clear the logged codes.

  Proceed to Test Step 4.

• Active code - One of the above codes is active. Proceed to Test Step 5.

Test Step 4. Use Cat ET to Check for Engine RPM

1. Observe "Engine Speed" on the status screen of Cat ET. Observe the "Engine Speed" parameter on the screen and set the engine control to the START position. Crank the engine.

2. Continue to observe the screen and allow the engine rpm to stabilize at the normal cranking speed.

3. Set the engine control to the COOLDOWN/STOP position.

Expected Result:

Before the engine is cranked, the engine speed is "0". The engine speed increases until the speed stabilizes at the normal cranking speed. When the engine is stopped, the speed decreases back to "0". A 320-3 diagnostic code or a 320-08 diagnostic code is not active.

Results:

• OK - The engine started and the engine ran properly. A 320-3 diagnostic code or a 320-8 diagnostic code was not active.

  Repair: The speed/timing sensor is operating properly. There may be an intermittent problem in the harness or in a connector. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Inspecting Electrical Connectors" for troubleshooting information.

  STOP

• Not OK - The engine cranked. However, Cat ET did not display the correct engine speed or a 320-3 or a 320-8 diagnostic code was activated. Proceed to Test Step 5.

• Not OK - The engine cranked but the engine did not start. Cat ET displayed the correct engine speed. A 320-3 diagnostic code or a 320-8 diagnostic code was not active. The ECM is receiving a valid signal.

  Repair: Refer to Troubleshooting, "Engine Cranks But Will Not Start". Perform the necessary repairs.

  STOP

Test Step 5. Measure the Sensor Supply Voltage at the Sensor

1. Set the engine control to the OFF position.

2. Install a 8T-8726 Adapter Cable As (3-PIN BREAKOUT) in series with the connectors for the speed/timing sensor.

3. Set the engine control to the COOLDOWN/STOP position. Measure the supply voltage between terminal "A" and terminal "B" of the breakout T.

Expected Result:

The supply voltage is 12.5 ± 1.0 VDC. A 145-3 diagnostic code or a 145-04 diagnostic code is not active.

Results:

• OK - The sensor is receiving correct supply voltage. A 145-03 diagnostic code or a 145-4 diagnostic code is not active. Leave the breakout T connected. Proceed to Test Step 6.

• Not OK - The sensor is not receiving correct supply voltage or a 145-3 diagnostic code or a 145-4 diagnostic code is active. Remove the breakout T. Proceed to Test Step 7.

Test Step 6. Isolate the Signal Voltage at the Sensor

1. Set the engine control to the OFF/RESET position.

2. Ensure that the breakout T is connected in series with the connectors for the speed/timing sensor.

3. Remove the wire from terminal "C" of the breakout T in order to isolate the sensor signal wire from the ECM.

4. Set the engine control to the COOLDOWN/STOP position. Measure the signal voltage between terminal "C" and terminal "B".

5. Set the engine control to the START position. Crank the engine and measure the signal voltage between terminal "C" and terminal "B".

Expected Result:

When the engine control is in the COOLDOWN/STOP position, the voltage is less than 3.0 VDC or the voltage is greater than 10.0 VDC.

The voltage varied between 2.0 VDC and 4.0 VDC during cranking.

Results:

• OK - The sensor is producing the correct output signal.

  Repair: Remove the breakout T from the connectors for the speed/timing sensor. Reconnect the connectors for the speed/timing sensor.

  Proceed to Test Step 8.

• Not OK - The sensor is not producing the correct output signal.

  Repair: Set the engine control to the OFF/RESET position.

  Remove the breakout T from the connectors for the speed/timing sensor.

  Install a new speed/timing sensor.

  STOP

Test Step 7. Measure the Sensor Supply Voltage at the ECM

1. Set the engine control to the OFF/RESET position.

2. Use two 7X-1710 Multimeter Probes. Insert the probes into terminal locations P1-43 and P1-51 at the ECM connector.

3. Set the engine control to the COOLDOWN/STOP position. Measure the supply voltage at the ECM.

Expected Result:

The voltage is 12.5 ± 1.0 VDC. A 145-3 diagnostic code or a 145-4 diagnostic code is not active.

Results:

• OK - The sensor supply voltage at the ECM is 12.5 ± 1.0 VDC. A 145-3 diagnostic code or a 145-4 diagnostic code is not active. The wiring and/or the connectors between the sensor and the ECM has an open circuit or the circuit has excessive resistance.

  Repair: Set the engine control to the OFF/RESET position. Perform the necessary repairs to the harness and/or connectors.

  STOP

• Not OK - The ECM is not producing the correct sensor supply voltage or a 145-3 or a 145-4 diagnostic code is active. There may be a problem with the ECM.

  Repair: Temporarily install a new ECM. Refer to Troubleshooting, "Replacing the ECM".

  If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP

Test Step 8. Measure the Sensor Signal Voltage at the ECM

1. Set the engine control to the OFF/RESET position.

2. Disconnect the J1/P1 ECM connectors.

3. Remove the wire from terminal location P1-33.

4. Connect the J1/P1 ECM connectors.

5. Set the engine control to the COOLDOWN/STOP position. Use two 7X-1710 Multimeter Probes in order to measure the signal voltage between terminals P1-33 and P1-51.

6. Set the engine control to the START . Crank the engine and measure the signal voltage between terminals P1-33 and P1-51.

Expected Result:

When the engine control is in the COOLDOWN/STOP position, the voltage is less than 3.0 VDC or the voltage is greater than 10.0 VDC.

The voltage varied between 2.0 VDC and 4.0 VDC during cranking.

Results:

• OK - The signal voltage is correct. However, the ECM is not reading the signal.

  Repair: There may be a problem with the ECM. Temporarily install a new ECM. Refer to Troubleshooting, "Replacing the ECM".

  If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP

• Not OK - The signal voltage is not correct. There is an intermittent problem in the circuit for the speed/timing sensor.

  Repair: Refer to Troubleshooting, "Inspecting Electrical Connectors". Make repairs, as needed.

  STOP