What Does P0955 Mean?
DTC P0955 is a general circuit malfunction code for the ASM mode selection circuit, which manages the driver-selectable transmission modes such as Performance, Winter, Sport, or Economy. The TCM detects a fault in the circuit connecting the mode selector switch to the control module, preventing proper mode identification or switching. The transmission may default to a standard operating mode.
Common Causes
30%
Faulty mode selector switch (worn contacts or internal failure)
25%
Wiring fault between the mode switch and TCM
20%
Corroded or damaged mode switch connector
15%
Mode switch ground circuit open or high resistance
10%
TCM mode input circuit failure
Diagnostic Steps
1
Step 1: Check if the mode indicator on the dashboard responds when switching between modes. If no response, the switch or circuit is likely at fault.
2
Step 2: Locate the mode selector switch (typically on the center console or gear selector) and inspect its connector for corrosion, loose pins, or damage.
3
Step 3: Test the mode switch continuity and resistance values in each position using a multimeter. Compare to the manufacturer's specification chart.
4
Step 4: Verify voltage supply and ground at the mode switch connector with the key on. If power is missing, trace the supply circuit for opens or blown fuses.
5
Step 5: If the switch tests good, check wiring continuity from the switch to the TCM. Look for opens or shorts along the harness route, especially under the console where wires can be pinched.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
DTC P0955 is a general circuit malfunction code for the ASM mode selection circuit, which manages the driver-selectable transmission modes such as Performance, Winter, Sport, or Economy. The TCM detects a fault in the circuit connecting the mode selector switch to the control module, preventing prop...
The most common cause of P0955 (ASM Mode Circuit [Perf / Winter / Sport / etc]) is: Faulty mode selector switch (worn contacts or internal failure)
Typical repair costs for P0955 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of mode selection is primarily a convenience issue. The transmission will continue to operate in a default mode. However, inability to select Winter mode in icy conditions or Sport mode when needed for spirited driving may reduce the driver's control over vehicle behavior.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0955 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission / Mode Selection
Difficulty
Type
Generic (SAE)
Recommended Tools
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