Isuzu 4JA1 Workshop Manual page 345

Step
2 1. Install the scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine and let idle for 30 seconds.
4. Monitor the Diagnostic Trouble Code (DTC)
Information with the scan tool.
Is DTC P0335 (Symptom Code B or D), P1335
(Symptom Code A) or P1345 (Symptom Code A)
set?
3 1. Turn OFF the engine.
2. Place the selector lever in P or N range and set
the parking brake.
3. Start the engine and let engine idle for 30
seconds while observing the Actual Injection
Timing parameter with the scan tool.
4. Accelerate the engine and keep the constant
engine speed around 2000 RPM while observing
the Actual Injection Timing parameter with the
scan tool.
5. Accelerate the engine and keep the constant
engine speed around 3000 RPM while observing
the Actual Injection Timing parameter with the
scan tool.
Does the Actual Injection Timing parameter follow
the Desired Injection Timing within 2°CA on each
engine speed?
4 1. Turn OFF the ignition.
2. Check the fuel system line connections between
the fuel tank and the fuel injection pump for
tightness and all fuel hoses for cuts, cracks and
for the use of proper clamps.
Notice: The fuel system from the fuel tank(s) to the
fuel injection pump is under a slight vacuum with the
engine running. As a result, air can enter the fuel
system if these connections are not tight. Air in the
fuel system will cause fuel injection pump internal
pressure fluctuations especially at high engine
speed and load, which may set this DTC.
3. Pump the priming pump on the fuel filter until it
becomes firm. If there is a leak on the suction
side of the fuel system between the priming
pump and the fuel injection pump, the priming
pump will not build up sufficient firmness and fuel
leakage may occur.
4. Repair or replace as necessary.
Did you find and correct the condition?
Action
Engine Control System (4JH1) 6E-91
Value(s) Yes

Go to Applicable
DTC

Go to Diagnostic
Aids

Go to Step 9
No
Go to Step 3
Go to Step 4
Go to Step 5