What Does P1605 Mean?
This code indicates the PCM's Keep Alive Memory (KAM) has failed an internal self-test. KAM is a section of volatile RAM that retains learned adaptive values (fuel trims, idle speed, shift points) while the ignition is off by maintaining power from the battery. A KAM test failure means the PCM cannot reliably store or recall these adaptive parameters, leading to poor drivability after each restart.
Common Causes
25%
Intermittent battery power loss or loose battery connection
25%
Blown or corroded PCM constant-power fuse (battery feed)
20%
PCM internal memory failure (capacitor or RAM chip degradation)
15%
Corroded or high-resistance PCM power supply connector pin
15%
Aftermarket alarm or accessory draining or interrupting PCM keep-alive power
Diagnostic Steps
1
Check the PCM keep-alive power fuse for corrosion or intermittent contact; measure voltage at the PCM battery-direct pin with the key off—it should show full battery voltage.
2
Inspect battery terminals and ground straps for looseness or corrosion that could cause intermittent power loss.
3
Check for aftermarket accessories wired into the PCM power circuit that may cause voltage drops or intermittent disconnections.
4
Perform a voltage drop test on the PCM constant power circuit from the battery positive terminal to the PCM pin.
5
If all power supply tests pass, the PCM may have an internal memory fault; reprogram or replace the PCM as needed.
6
Clear the code and monitor for recurrence; an intermittent battery disconnect may take time to reproduce.
Estimated Repair Cost
$50 - $800
Parts + labor, varies by vehicle and location
This code indicates the PCM's Keep Alive Memory (KAM) has failed an internal self-test. KAM is a section of volatile RAM that retains learned adaptive values (fuel trims, idle speed, shift points) while the ignition is off by maintaining power from the battery. A KAM test failure means the PCM canno...
The most common cause of P1605 (Powertrain Control Module Keep Alive Memory Test Error) is: Intermittent battery power loss or loose battery connection
Typical repair costs for P1605 range from $50 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of KAM causes the PCM to reset all learned values on each restart, resulting in rough idle, poor shift quality, and reduced fuel economy until the values are relearned. Not an immediate driving hazard but degrades overall vehicle performance.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1605 to identify the root cause.
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Quick Info
Category
Powertrain
System
PCM / Engine Management
Difficulty
Type
Manufacturer
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