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The code P1633 is caused by a loss of keep alive power source to the PCM (engine computer).This power source helps the PCM keep in memory the operations of the engine and transmission.If you had a low battery,disconnected PCM or had a lose connection in the power circuit,you can set this code.
Note: If KAPWR is interrupted to the PCM (that is, when a breakout box is installed or the battery is disconnected), DTC P0603 can be generated on the first power-up.
Are the battery terminal connections in good condition?
Is wiring too close to ignition components or wires?
Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.
Does the voltage reading indicate less than 10.5 volts?
Is DTC P0603 or P1633 present?