sorry the code was P1603-PCM INTERNAL DUAL-PORT RAM COMMUNICATION FAILURE and on alldata they said causes are
PCM fused ignition switch circuit
1. PCM IGNITION CIRCUITS
Turn the ignition off.
Disconnect the PCM harness connectors.
Ignition on, engine not running.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.
With a 12-volt test light connected to ground and with special tool #8815 installed, probe the (F202) and (F924) Fused Ignition Switch circuits.
Perform the above check with the Ignition key in the off lock position, Ignition on, engine not running position, and during cranking.
Wiggle the related wire harness while probing the special tool with the test light to try to interrupt the circuit.
Q: Does the test light illuminate brightly?
YES: Go To 2
NO: Repair the open or excessive resistance in the (F202) and (F924) Fused Ignition Switch (Off, Run, Start) circuits. Inspect the related fuse, if the fuse is open check the circuits for a short to ground. Perform the POWERTRAIN VERIFICATION TEST. See: Verification Tests Powertrain Verification Test
and I dont know where is those circuits (F202) and (F924)
Tuesday, May 5th, 2015 AT 9:58 AM