0314817 JOHNSON BY-PASS COVER,Upper

Table 1
Diagnostic Codes Table
Code and Description Conditions which Generate this Code System Response
41-3 8 Volt DC Supply : Voltage Above Normal The 8 volt power supply is above normal for two seconds. The code is logged.
The alarm output is activated.
The shutdown output is activated.
The engine is shut down.
41-4 8 Volt DC Supply : Voltage Below Normal The 8 volt power supply is below normal for two seconds.
262-3 5 Volt Sensor DC Power Supply : Voltage Above Normal The 5 volt power supply is above normal for two seconds.
262-4 5 Volt Sensor DC Power Supply : Voltage Below Normal The 5 volt power supply is below normal for two seconds. 5 Volt Power SupplyThe Electronic Control Module (ECM) supplies 5.0 0.5 VDC to these sensors:
Engine oil temperature
Filtered engine oil pressure
Inlet air temperature
Throttle valve differential pressure
Unfiltered engine oil pressureThe ECM also provides 5.0 0.5 VDC to the speed control potentiometer (if equipped).The internal circuits for J1-2 (sensor supply) and J1-18 (speed control supply) are wired to the same voltage source inside the ECM. A short circuit on one of these terminals will cause a short circuit on the other terminal. A 262-4 5 Volt Sensor DC Power Supply voltage below normal will be activated if the following conditions occur:
The desired speed signal wire is shorted to ground.
The speed control potentiometer is near the maximum desired speed or at the maximum desired speed.A diagnostic code for the 5 volt power supply is probably caused by a short circuit or by an open circuit in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.
Illustration 1 g01771939
Schematic for the 5 volt power supply
8 Volt Power SupplyThe ECM supplies 8.0 0.8 VDC to these sensors:
Engine coolant pressure sensor (outlet)
Intake manifold pressure sensorThe ECM also supplies 8.0 0.8 VDC to the detonation sensors for the left side of the engine.The internal circuits for J1-4, J2-56, and J2-57 are wired to the same voltage source inside the ECM. A short circuit on one of these terminals will cause a short circuit on the other terminals.A diagnostic code for the 8 volt supply is probably caused by a short circuit or by an open circuit in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with an ECM.
Illustration 2 g01772033
Schematic for the detonation sensors that are powered by the 8 volt supply
Illustration 3 g01771774
Schematic for the PWM sensors that are powered by the 8 volt supply
Test Step 1. Inspect the Electrical Connectors and the Wiring
Set the engine control to the OFF/RESET position. Remove the electrical power from the engine.
Illustration 4 g01772173
Locations of the engine sensors that are associated with the sensor supply circuits (typical right and left side engine views)
(1) Intake manifold air temperature sensor
(2) Intake manifold pressure sensor
(3) Engine oil temperature sensor
(4) Pressure sensor for unfiltered oil
(5) Pressure sensor for filtered oil
(6) Engine coolant pressure sensor (outlet)
(7) Throttle valve differential pressure sensor
(8) Detonation sensors (right side)
(9) Detonation sensors (left side)
Illustration 5 g01772193
Locations of the connectors at the ECM junction box that are for the sensor supply circuits
(10) J2/P2 ECM connectors
(11) J1/P1 ECM connectors
(12) Control harness connectors
(13) Connectors for the detonation sensor harness
Illustration 6 g01772194
Locations of the connectors at the engine junction box that are for the sensor supply circuits
(14) Engine interface connectors
(15) Interconnect harness connectors
Thoroughly inspect the condition of the connectors that are for sensors (1 through 9). Inspect the condition of connectors (10 through 13) that are located at the ECM junction box. Also, thoroughly inspect the condition of connectors (14) and (15) that are located at the engine junction box. Refer to Troubleshooting, "Electrical Connectors - Inspect".
Illustration 7 g01417594
Terminal locations at the P1 ECM connector that are for the sensor supply circuit
(P1-2) 5 volt supply for the engine sensors
(P1-3) Return for the 5 volt engine sensors
(P1-4) 8 volt supply for the engine sensors
(P1-5) Return for the 8 volt engine sensors
(P1-18) 5 volt supply for the desired speed potentiometer
(P1-35) Return for the desired speed potentiometer
Illustration 8 g01417617
Terminal locations at the P2 ECM connector that are for the sensor supply circuit
(P2-54) Return for the 8 volt detonation