Pgm-Fi Troubleshooting Information - Honda TRX680FA Service Manual

FUEL SYSTEM (PGM-FI)
PGM-FI TROUBLESHOOTING INFORMATION
GENERAL TROUBLESHOOTING
Intermittent Failure
The term "intermittent failure" means a system may have had a failure, but it checks OK now. If the MIL does not come on,
check for poor contact or loose pins at all connectors related to the circuit with the trouble. If the MIL was on, but then went
out, the original problem may be intermittent.
Opens and Shorts
"Opens" and "Shorts" are common electrical terms. An open is a break in a wire or at a connection. A short is an accidental
connection of a wire to ground or to another wire. In simple electronics, this usually means something will not work at all.
With PCMs this can mean something will work, but not the way it's supposed to.
If the MIL has come on
Refer to DTC READ OUT (page 6-14).
If the MIL did not stay on
If the MIL did not stay on, but there is a driveability problem, do the SYMPTOM TROUBLESHOOTING (page 6-5).
SYSTEM DESCRIPTION
SELF-DIAGNOSIS SYSTEM
The PGM-FI system is equipped with the self-diagnostic system. When any abnormality occurs in the system, the PCM
turns on the MIL and stores a DTC in its erasable memory.
FAIL-SAFE FUNCTION
The PGM-FI system is provided with a fail-safe function to secure a minimum running capability even when there is trouble
in the system. When any abnormality is detected by the self-diagnosis function, running capability is maintained by pre-
programed value in the simulated program map. When any abnormality is detected in the injector and crankshaft position
(CKP) sensor, the fail-safe function stops the engine to protect it from damage.
DTC (Diagnostic Trouble Code)
• The DTC is composed of a main code and a sub code and it is displayed as a hyphenated number when retrieved from
the PCM with the HDS pocket tester.
The digits in front of the hyphen are the main code, they indicate the component of function failure.
The digits behind the hyphen are the sub code, they detail the specific symptom of the component or function failure.
For example, in the case of the TP sensor:
- DTC 08 - 1 = (TP sensor voltage) - (lower than the specified value)
- DTC 08 - 2 = (TP sensor voltage) - (higher than the specified value).
• The MAP, ECT, TP and IAT sensor diagnosis will be made according to the voltage output of the affected sensor.
If a failure occurs, the PCM determines the Function Failure, compares the sensor voltage output to the standard value,
and then outputs the corresponding DTC to the HDS Pocket Tester.
For example:
- If the input voltage line (A) on the MAP sensor is opened, the PCM detects the output voltage is about 5 V, then the
DTC 1-2 (MAP sensor circuit high voltage) will be displayed.
- If the input voltage line (B) on the TP sensor is opened, the PCM detects the output voltage is 0 V, then the DTC 8-1 (TP
sensor circuit low voltage) will be displayed.
5V
MAP SENSOR
TP SENSOR
OUTPUT VOLTAGE
5V
OUTPUT VOLTAGE
ECT SENSOR
5V
I
IAT SENSOR
OUTPUT VOLTAGE
5V
OUTPUT VOLTAGE
h.
6-13