Circuit Description:
During cranking, the ignition module monitors the dual crank sensor 3X signal. The 3X signal is used to determine the correct cylinder pair to spark first. After the 3X signal has been processed by the ignition module, it sends a crankshaft reference pulse to the PCM. When the PCM receives this pulse it will command all six injectors to open for one priming shot of fuel in all cylinders. After the priming, the injectors are left "OFF" for the next six crankshaft reference pulses from the ignition module (two crankshaft revolutions). This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, a cam signal will have been received by the PCM. Now the PCM begins to operate the injectors by energising each injector based on true camshaft position. With the engine running, the PCM monitors the cam and 18X signal pulses it receives and expects to see 36 18X signal pulses for each cam pulse. If the sequence of pulses is not correct for 15 occurrences, DTC 49 will set, indicating an intermittent problem with the cam signal or 18X signal "reference" signal.
Test Description: Number(s) below refer to step number(s) on the diagnostic chart.
2. Determines if conditions necessary to set DTC 49 exist on this ignition cycle.
3. If 5 volts are not present at PCM harness connector terminal "D3", the cam sensor may be interfacing with the magnet in the camshaft sprocket. Bumping the starter should correct this condition.
6. If a failure is induced in the 18X signal circuit, the 5 volts on the circuit should change when the faulty wiring or connection is manipulated.
NOTE: If DTC 48 is set along with DTC 49, use DTC 48 chart for diagnosis.
Diagnostic Aids:
DTC 49 indicates an intermittent fault and may not set immediately or under all conditions. Customer comments of symptoms experienced may help isolate the cause of the condition. A poor connection or fault in the cam sensor circuits 630, 633, 644, or 645 or a faulty cam sensor may cause the PCM to re-initialise injector sequence when the fault occurs, causing a possible stumble or miss. A poor connection or fault in the 18X signal circuit 647, crank sensor circuits 643, 644, or 645, the 18X portion of the crank sensor or bent or missing vanes on the harmonic balancer interrupter rings will cause the PCM to stop pulsing the injectors when the fault occurs, causing an intermittent stumble or stall.
