Code 647 is a fuel trim problem. Before checking both codes need to verify ECU connector and harness are good. Make sure there are no breaks or damage.
Verify fuel quality. Inspect gasoline for contaminants or verify LP is certified HD-5 or HD-10 and there are no
known fuel issues.
Is fuel contaminated?
YES: Replace with correct / certified LP. Drain gasoline, flush system, and use new fuel source.
NO: Proceed to Step 2.
2. Inspect fuel delivery system for leaks or damage. Inspect storage tank, delivery lines, rails, and other fuel
components.
Is fuel system damage evident?
YES: Repair fuel system / component, clear DTC and retest system.
Inspect exhaust system components for damage. Ensure no restrictions or leaks are present.
Is an exhaust fault present?
YES: Repair or replace exhaust system, clear DTC and retest system.
Inspect air filter and air induction system. Ensure no damage or restrictions are present.
Is an air restriction present?
YES: Repair or replace faulty air induction component.
If no faults are evident and fault code remains, replace faulty mixer or fuel regulator.
For code 693, follow directions below.
Disconnect ECU connector CRS202 and measure voltage between socket 60 or 79 and B(-).
Is battery voltage present?
YES: Disconnect battery and proceed to Step 2.
NO: Inspect ECU power circuits 005-A and 005-B for open or short.
2. Measure resistance between CRS202, socket 81 and B(-).
Is resistance = 1 ohm?
YES: Connect battery and proceed to CAUSE B.
NO: Inspect ground circuit 126-Z and 126-E for open, short, or source of excessive resistance
Measure voltage between the ECU connector CRS202, socket 14 and B(-).
Is CAN HI voltage approximately 2.5 Vdc?
YES: Proceed to Step 2.
NO: Inspect CAN HI circuit for open or short. If voltage is 0 volts, the CAN HI circuit is shorted to ground or
open. If voltage is above 5 volts, the CAN HI circuit is shorted to power.
2. Measure voltage between the ECU connector CRS202, socket 15 and B(-).
Is CAN LO voltage approximately 2.5 Vdc?
YES: Disconnect battery and proceed to Step 3.
NO: Inspect CAN LO circuit for open or short. If voltage is 0 volts, the CAN LO circuit is shorted to ground or
open. If voltage is above 5 volts, the CAN LO circuit is shorted to power.
3. Measure resistance between the ECU connector CRS202, socket 14 and socket 15.
Is resistance 60 ± 6 ohms?
YES: No communication faults are present, connect battery and proceed to CAUSE C.
NO: If resistance is 120 ohms, the CANbus has an open circuit or a missing or damaged termination resistor.
If resistance is 0 ohms, the CANbus circuits are shorted together.