DTC P0603, P1605, P1633 DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0603, P1605, P1633	POWERTRAIN CONTROL MODULE (PCM) MALFUNCTION
DETECTION CONDITION	P0603 and P1605 indicate that the PCM has experienced a power interrupt in the Keep Alive Power (KAPWR) circuit or an internal memory test failure. However there are external items that can cause the DTC. P1633 indicates that the Keep Alive Power (KAPWR) circuit has experienced a power interrupt.
POSSIBLE CAUSE	Battery terminal corrosion or loose connections (P0603, P1605). Open KAPWR circuit (P1633). KAPWR to PCM interrupt/open (P0603, P1605). Damaged PCM (P0603, P1605, P1633). Reprogramming (P0603, P1605). Intermittent KAPWR circuit (P1633). Improper KAPWR circuit wire routing.
HINT	PCM Description Receives information from a variety of sensors and switch inputs. Based on the strategy and calibration stored within the memory chip, the PCM generates the appropriate output. The system is designed to minimize emissions and optimize fuel economy and driveability. The software strategy: Controls the basic operation of the engine and transmission. Provides the OBD II strategy. Controls the malfunction indicator lamp (MIL). Communicates to the NGS Tester via the data link connector (DLC). Allows for Flash Electrically Erasable Programmable Read Only Memory (FEE-PROM). Provides idle air and fuel trim. Controls Failure Mode Effects Management (FMEM).

DTC P0603, P1605, P1633 INSPECTION

STEP	INSPECTION		ACTION
1	Was PCM Quick Test performed?	Yes	Go to next step.
1	Was PCM Quick Test performed?	No	Perform PCM Quick Test.
2	CHECK BATTERY TERMINALS NOTE: If KAPWR is interrupted to the PCM (that is, when a Breakout Box is installed or the battery is disconnected), DTCs P0603/P1605 can be generated on the first power-up. Inspect the battery cables for loose connections, corrosion. Are the battery terminal connections in good condition?	Yes	Go to next step.
2		No	Repair battery terminals as necessary. Go to step 5.
3	INSPECT ENGINE COMPARTMENT FOR PROPER WIRE ROUTING Inspect engine compartment wiring for proximity to ignition components or wires. Is wiring too close to ignition components or wires?	Yes	Reroute wires as necessary. Go to step 5.
3		No	Engine compartment wire routing is OK. Go to next step.
4	CHECK KEEP ALIVE POWER (KAPWR) TO PCM Disconnect PCM. Install Breakout Box, leave PCM disconnected. Measure voltage between PCM test pin 55 (KAPWR) and PCM test pin 103 (PWR GND). While observing multimeter, grasp the engine harness and wiggle, shake or bend a small section while working from the PCM to the dash panel. Does the voltage reading indicate less than 10.5 V?	Yes	Isolate and repair open in KAPWR circuit. Go to step 5.
4		No	No open in KAPWR harness circuit detected. Go to step 5.
5	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Make sure to reconnect all disconnected connectors. Clear DTCs from PCM memory using NGS tester generic OBD-II function. Perform PCM Quick Test. Is same DTC present?	Yes	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Repeat PCM Quick Test.
5		No	If any other DTC is present, go to applicable DTC inspection. If no DTC is present, troubleshooting complete.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Powertrain Control Module (Pcm) Malfunction

Use the Manual With the Right Hardware

When to See a Mechanic

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