What Does P1596 Mean?
This code indicates the automatic transmission diagnosis input signal circuit is reading a voltage that exceeds the maximum expected threshold. This is the high-input variant, typically caused by an open circuit, disconnected sensor, or wiring fault that allows the signal to float high or be pulled up to reference voltage. The PCM cannot accurately determine the transmission's operating status.
Common Causes
30%
Open circuit in the transmission input signal wiring
25%
Disconnected or loose transmission electrical connector
20%
Failed internal transmission sensor with open circuit
15%
Broken wire in the harness between transmission and PCM
10%
Corroded connector pins creating an open-circuit condition
Diagnostic Steps
1
Verify the transmission electrical connector is fully seated and locked; a partially engaged connector is a common cause.
2
Monitor the transmission diagnosis input signal on live data; confirm it reads above the expected maximum.
3
Check for continuity from the PCM to the transmission connector on the signal wire; an open indicates a wiring break.
4
Inspect the transmission connector pins for pushed-back, bent, or corroded contacts that may not make proper electrical connection.
5
If external wiring is intact, the fault may be an internal transmission sensor or harness requiring valve body access.
Estimated Repair Cost
$150 - $900
Parts + labor, varies by vehicle and location
This code indicates the automatic transmission diagnosis input signal circuit is reading a voltage that exceeds the maximum expected threshold. This is the high-input variant, typically caused by an open circuit, disconnected sensor, or wiring fault that allows the signal to float high or be pulled ...
The most common cause of P1596 (Automatic transmission diagnosis input signal circuit high input) is: Open circuit in the transmission input signal wiring
Typical repair costs for P1596 range from $150 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The transmission may operate in limp mode or exhibit erratic shifting. High-input faults often cause the PCM to default to a safe operating strategy that limits shift range and torque converter lockup.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1596 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission
Difficulty
Type
Manufacturer
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