Check the ECM fuse, if fuse is OK try erasing the code first and if the code comes back you may have to reprogram or replaced the ECM.
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How to Fix the DTC P0604 2004 Toyota Highlander?
Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
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What is the Cost to Diagnose the Code?
Labor: 1.0
The cost to diagnose the P0604 2004 Toyota Highlander code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.
When is the Code Detected?
Indicates the ECM has experienced an internal memory fault.
What are Code Possible Symptoms?
Engine Light ON (or Service Engine Soon Warning Light)
Engine may not start
What Does the P0604 2004 Toyota Highlander Code Mean?
The Engine Control Module (ECM) continuously monitors its internal memory status, internal circuits, and output signals to the throttle actuator. This self−check insures that the ECM is functioning properly. If any malfunction is detected, the ECM will set the code and illuminate the engine light.
The ECM memory status is diagnosed by internal mirroring of the main CPU and the sub CPU to detect Random Access Memory (RAM) errors. The two CPUs also perform continuous mutual monitoring. The ECM illuminates the MIL and sets a DTC if: 1) outputs from the two CPUs are different or deviate from the standards, 2) the signals sent to the throttle actuator deviate from the standards, 3) a malfunction is found in the throttle actuator supply voltage, and 4) any other ECM malfunction is found.
P0604 2004 Toyota Highlander Code - Internal Control Module Random Access Memory Error