the cat nissan systems had some issues with this code also
here are some of the issues that caused this code in their trucks
- DTC E43 ( P1815 ) Description: LPG air-fuel ratio malfunction.
- This engine has a long crank time before starting. Mass air flow sensors when bad can cause the ECM to change crank time electronically. Mass air flow meter failure.
- Assistant injector leaking or a pressure relief spring stuck. found the assistant injector was bad.
- Intake manifold cracked or loose bolts.
- Main injector o-ring installed backwards
- Injector Holder in some cases caused code.
check these things and see what you come up with (some of this looks as if you already have done but it doesn't hurt to recheck them)
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