engine pressure sensor open or short .pdf

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Product: WHEEL LOADER

Model: 966H WHEEL LOADER A6D

Configuration:966H Wheel Loader A6D00001-UP (MACHINE) POWERED BY C11 Engine Troubleshooting

C11 and C13 Engines for Caterpillar Built Machines

Media Number -RENR9318-11 Publication Date -01/12/2013 Date Updated -12/12/2013

i02402329

Engine Pressure Sensor Open or Short Circuit - Test

SMCS - 1439-038-PX

System Operation Description:

Use this procedure to troubleshoot any suspect problems with the following sensors: Fuel pressure sensor

•

Engine oil pressure sensor •

Atmospheric pressure sensor •

Right turbo inlet pressure sensor •

Intake manifold pressure sensor •

Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:

94-03 Fuel Pressure open/short to +batt •

94-04 Fuel Pressure short to ground •

100-03 Engine Oil Pressure open/short to +batt •

100-04 Engine Oil Pressure short to ground •

274-03 Atmospheric Pressure open/short to +batt •

274-04 Atmospheric Pressure short to ground •

03/03/2014 https://sis.cat.com/sisweb/sisweb/techdoc/techdoc_print_page.jsp?returnurl=/sisweb/sisw...

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275-03 Right Turbo Inlet Pressure open/short to +batt •

275-04 Right Turbo Inlet Pressure short to ground •

1785-03 Intake Manifold Pressure Sensor voltage high •

1785-04 Intake Manifold Pressure Sensor voltage low •

The 5 volt sensor supply provides power to all 5 volt sensors. The Electronic Control Module (ECM) supplies 5.0 ± 0.2 VDC to terminal A of each sensor connector. The sensor return from the ECM connector goes to terminal B of each sensor connector. The sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM.

Pull-up Voltage

The ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect a problem in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal circuit, the ECM will generate a 03 diagnostic code for the sensor.

If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the wires from the sensor connector to the ECM are OK. If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates a problem in the signal wire. If the sensor is disconnected at the sensor connector and the voltage at the sensor connector is different from pull-up voltage, the signal wire may be shorted to another wire in the harness.

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Illustration 1 g01203122 Schematic for the engine pressure sensors

Test Step 1. Inspect the Electrical Connectors and the Wiring Remove electrical power from the engine ECM.

A.

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Illustration 2 g01200216 Locations of the pressure sensors (typical left side engine view)

(1) Atmospheric pressure sensor (2) Fuel pressure sensor

(3) Intake manifold pressure sensor (4) Engine oil pressure sensor (5) J2/P2 ECM connectors (6) J1/P1 ECM connectors

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Illustration 3 g01142856 Air filter assembly

(7) Right turbo inlet pressure sensor

Thoroughly inspect connector (5) and (6). Also, thoroughly inspect the connectors for sensors (1), (2), (3), (4) and (7). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. B.

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Illustration 4 g01024457 P2 ECM connector

(P2-15) Intake manifold pressure sensor (P2-17) Sensor return

(P2-28) Engine oil pressure sensor (P2-40) Fuel pressure sensor (P2-57) Atmospheric pressure sensor (P2-72) Sensor supply

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Illustration 5 g01145897 P1 ECM connector

(P1-2) Sensor supply (P1-3) Sensor return

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(P1-15) Right turbo inlet pressure sensor

Illustration 6 g01159881

Sensor connector (A) Sensor supply (B) Sensor return (C) Signal

Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and on each of the wires in the pressure sensor connectors.

C.

Check the allen head screw for each of the ECM connectors and the machine connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

D.

Check the harness and wiring for abrasions and for pinch points from each of the pressure sensors back to the ECM.

E.

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 wiring appear to be OK. Proceed to Test Step 2. •

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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 for each of the connectors are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.

STOP

Test Step 2. Check the Supply Voltage at the Sensor Connector Remove electrical power from the engine ECM.

A.

Disconnect the harness connectors for the following sensors: B.

Fuel pressure sensor ◦

Engine oil pressure sensor ◦

Intake manifold pressure sensor ◦

Atmospheric pressure sensor ◦

Right turbo inlet pressure sensor ◦

Restore electrical power to the engine ECM. C.

Note: The original diagnostic code may not stay active. An open circuit diagnostic code for the sensor supply may become active when all of the sensors are disconnected. Ignore the active codes at this time and continue with this test step.

Note: Be sure to wiggle the harness during the following measurements in order to reveal an intermittent condition.

Measure the voltage between terminals A and B at each sensor connector on the engine harness. D.

Remove electrical power from the engine ECM. E.

Connect all of the sensors. F.

Expected Result:

Each voltage measurement is 5.0 ± 0.2 VDC. Results:

OK - Each voltage measurement is 5.0 ± 0.2 VDC. The voltage is correct at the sensor connectors. Proceed to Test Step 3.

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Not OK - The voltage is not 5.0 ± 0.2 VDC. The voltage is incorrect. •

Repair: Perform the diagnostic functional test Troubleshooting, "5 Volt Engine Pressure Sensor Supply Circuit - Test".

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STOP

Test Step 3. Check for Active Diagnostic Codes

Connect Caterpillar Electronic Technician (ET) to the service tool connector. A.

Restore electrical power to the engine ECM. B.

Note: Wait at least 30 seconds so that any codes may become active.

Monitor the active diagnostic code screen on Cat ET. Look for an active diagnostic code for an engine pressure sensor.

C.

Determine if the problem is related to an open circuit diagnostic code 03 or a short circuit diagnostic code 04.

D.

Expected Result:

No diagnostic codes are active. Results:

OK - No diagnostic codes are active for the engine pressure sensors. •

Repair: The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. Refer to Troubleshooting, "Electrical Connectors -Inspect".

STOP

Not OK - A 03 diagnostic code is active at this time. Proceed to Test Step 5. •

Not OK - A 04 diagnostic code is active at this time. Proceed to Test Step 4. •

Test Step 4. Disconnect the Suspect Sensor in Order to Create an Open Circuit Remove electrical power from the ECM.

A.

Disconnect the harness connector of the sensor with the 04 diagnostic code. B.

Restore electrical power to the ECM. C.

Use Cat ET to check for active diagnostic codes. Wait at least 30 seconds for activation of the diagnostic codes. Check for an active 03 diagnostic code for the disconnected sensor.

D.

Remove electrical power from the ECM. E.

Expected Result:

A 04 diagnostic code was active before the sensor was disconnected. A 03 diagnostic code became active after the sensor was disconnected.

Results:

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OK - A 04 diagnostic code was active before the sensor was disconnected. A 03 diagnostic code became active after the sensor was disconnected.

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Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

STOP

Not OK - When the sensor is disconnected, a 04 diagnostic code remains active for the suspect sensor. There is a short circuit between the sensor harness connector and the ECM. Leave the sensor disconnected. Proceed to Test Step 6.

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Test Step 5. Create a Short at the Suspect Sensor Connector Remove electrical power from the engine ECM.

A.

Fabricate a jumper wire that is long enough to connect two terminals at the sensor connector. Crimp connector sockets to each end of the jumper wire.

B.

Install the jumper wire between terminal B (sensor return) and terminal C (sensor signal) on the harness side of the connector for the suspect sensor.

C.

Restore electrical power to the engine ECM. D.

Note: Wait at least 30 seconds for activation of the diagnostic code.

Monitor the "Active Diagnostic Codes" screen on Cat ET before installing the jumper wire and after installing the jumper wire.

E.

Check for an active short circuit diagnostic code 04 while the jumper wire is installed. Remove electrical power from the engine ECM.

F.

Remove the jumper wire. G.

Expected Result:

A 04 diagnostic code was active when the jumper wire was installed. A 03 diagnostic code became active when the jumper wire was removed.

Results:

OK - A 04 diagnostic code was active when the jumper wire was installed. A 03 diagnostic code became active when the jumper wire was removed.

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Repair: The engine harness and the ECM are OK. Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

STOP

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Not OK - The 03 diagnostic code remains active with the jumper in place. There is a problem in the circuit between the ECM and the sensor connector. There may be a problem with the ECM. Proceed to Test Step 6.

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Test Step 6. Test the Operation of the ECM

Remove electrical power from the engine ECM. A.

Fabricate a jumper wire that is long enough to connect one of the terminals at the ECM connector to the engine ground stud. Crimp a connector socket to one end of the jumper wire. B.

Disconnect the appropriate ECM connector for the signal wire of the suspect sensor. C.

Remove the signal wire for the suspect sensor from the ECM connector. D.

Install the jumper wire into the terminal location of the suspect sensor's signal wire at the ECM connector.

E.

Connect the ECM connectors. F.

Check the operation of the ECM by creating an open at the ECM: G.

Hold the loose end of the jumper wire away from any components in order to create an open circuit condition.

a.

Restore electrical power to the engine ECM. b.

Note: Wait at least 30 seconds so that any codes may become active. Monitor the "Active Diagnostic Code" screen on Cat ET.

c.

Check the suspect sensor for an active 03 diagnostic code. Remove electrical power from the engine ECM.

d.

Check the operation of the ECM by creating a short circuit at the ECM: H.

Connect the jumper wire to the engine ground stud. a.

Restore electrical power to the engine ECM. b.

Note: Wait at least 30 seconds so that any codes may become active. Monitor the "Active Diagnostic Code" screen on Cat ET.

c.

Check the suspect sensor for an active 04 diagnostic code while the jumper wire is installed.

d.

Remove electrical power from the engine ECM. e.

Remove the jumper wire. Return all wiring to the original configuration. I.

Expected Result:

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A 03 diagnostic code is active when the sensor signal wire is removed from the ECM connector. A 04 diagnostic code is active when the signal wire is connected to the engine ground stud.

Results:

OK - A 03 diagnostic code is active when the sensor signal wire is removed from the ECM connector. A 04 diagnostic code is active when the signal wire is connected to the engine ground stud.

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Repair: The ECM is operating properly. The problem is in the harness wiring between the ECM and the sensor connector. If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor. Repair the return wire for the sensor or replace the harness.If the code is only active for one sensor, the problem is most likely in the signal wire for the sensor. Repair the signal wire for the sensor.

STOP

Not OK - One of the following conditions exists: The 03 diagnostic code is not active when the sensor signal wire is disconnected. The 04 diagnostic code is not active when the wire jumper is installed.

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Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

STOP

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Mon Mar 3 17:37:40 EST 2014 r080nr1