121A3-ZV0-300 Honda GUIDE, VALVE (OS) (Honda Code 1871896).

Table 1
Diagnostic Codes Table
Code and Description Conditions which Generate this Code System Response
827-8 Left Exhaust Temperature Sensor : Abnormal Frequency, Pulse Width, or Period The Electronic Control Module (ECM) detects a sensor frequency that is greater than 1000 Hz or less than 150 Hz.
The ECM detects a duty cycle that is greater than 90 percent or a duty cycle that is less than 10 percent. The value of the parameter is set to zero.
The code is logged.
828-8 Right Exhaust Temperature Sensor : Abnormal Frequency, Pulse Width, or Period The ECM detects a sensor frequency that is greater than 1000 Hz or less than 150 Hz.
The ECM detects a duty cycle that is greater than 90 percent or a duty cycle that is less than 10 percent. System OperationBoth the primary ECM and the secondary ECM can provide digital power and digital sensor reference to the engine sensors. In normal operation, the primary ECM has control of the engine. The primary ECM will provide the digital power and the digital sensor reference to the engine sensors. If the secondary ECM must take over control of the engine, the secondary ECM will provide digital power and the digital sensor reference to the engine sensors.The power to the engine sensors is switched between the primary ECM and secondary ECM by the relay panel that is mounted on the left side of the engine. When the secondary ECM assumes control of the engine, the sinking driver for the "Backup ECM Active Lamp" is activated. When the sinking driver for the "Backup ECM Active Lamp" is activated, the 8 V power relay in the relay panel is energized. When the 8 V power relay is energized, the digital power to the engine sensors is switched from the primary ECM to the secondary ECM.The digital sensor reference to the engine sensors is switched between the primary ECM and secondary ECM by the "RSR" relay that is mounted in the control panel. When the secondary ECM assumes control of the engine, the sinking driver for the "Backup ECM Active Lamp" is activated. When the sinking driver for the "Backup ECM Active Lamp" is activated, the "RSR" relay in the control panel is energized. When the "RSR" relay is energized, the digital digital sensor reference to the engine sensors is switched from the primary ECM to the secondary ECM.The "Pulse Width Modulated (PWM)" sensors provide a signal to the engine's ECM. The sensors receive a 8.0 0.4 VDC regulated voltage from the ECM.The sensor's wires are routed from the ECM to the sensor connectors. The following list gives the terminal locations for the sensor connector.
Terminal A 8 V digital sensor supply
Terminal B Digital sensor reference
Terminal C Sensor signalThe ECM performs an automatic calibration of these sensors whenever the ECM is powered and the engine has been off for at least five seconds.The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.
Illustration 1 g01627272
Typical schematic
Illustration 2 g01627273
P1 ECM connector
(P1-4) "8 V digital sensor supply"
(P1-5) "Digital sensor reference"
(P1-11) Left exhaust temperature
(P1-12) Right exhaust temperature
(P1-55) +Battery (secondary ECM)
(P1-57) +Battery (primary ECM)
Illustration 3 g01628974
P2 ECM connector
(P2-29) "Backup ECM Active Lamp"
Illustration 4 g01327759
Terminal locations for the A-C1/E-C2/E-C1 Right hand cross over harness
(Terminal C) "8 V digital sensor supply"
(Terminal D) "Digital sensor reference"
(Terminal R) "Right exhaust temperature"
Illustration 5 g01622856
Connector locations
(1) A-C1/E-C2/E-C1 Right hand cross over harness
(2) A-C2/J-C2/J-C1 Right hand cross over harness
(3) A-C90/P-C1 Connectors for the power distribution panel
(4) A-C91/P-C2 Connectors for the power distribution panel
(5) A-C60 Connector for the prelube motor
(6) A-C92/F-C1/F-C2/G-C6 Connectors for a RH Control panel
(7) C-C22 Primary ECM connector P2
(8) C-C15 Primary ECM connector P1
(9) C-C28 Secondary ECM connector P2
(10) C-C29 Secondary ECM connector P1
(11) C-C47 Connector for the power relay panel
(12) C-C17/F-C1/F-C2/G-C6 Connectors for a LH Control panel
(13) C-C18/(TB-C1 customer or L-C1/L-C2 EMCP 3) connectors
(14) C-C2/J-C1/J-C2 Left hand cross over harness
(15) C-C1/E-C1/E-C2 Left hand cross over harness
Illustration 6 g01234146
Location of ECM connectors
Illustration 7 g01094844
Sensor connector
(Pin A) Sensor supply
(Pin B) Sensor return
(Pin C) Signal Test Step 1. Check for an "Active" Diagnostic Code
Turn the ECS to the OFF position.
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the ECS to the STOP position.
Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Determine if a diagnostic code has occurred several times. Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal.
Determine if a 8 diagnostic code is active for one of the exhaust temperature sensors: Expected Result:No diagnostic code is active for the exhaust temperature sensors.Results:
OK - No diagnostic codes are acti