P0956 Fault Code

ASM Mode Circuit Range/Performance

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0956 fault code refers to an issue with the ASM (Automatic Shifting Mechanism) mode circuit, indicating that the circuit is out of the expected range or is not performing as intended. This can disrupt the vehicle's shifting capabilities, potentially leading to poor performance or drivability issues. Understanding this code is crucial for diagnosing transmission problems effectively.

What are the symptoms of the P0956 code?

Common symptoms associated with the P0956 fault code include:

• Transmission not shifting properly or staying in gear.
• Slipping or hesitation during acceleration.
• Warning lights on the dashboard, such as the check engine light.
• Unresponsive shifting after engaging the transmission selector.
• Harsh or delayed engagement when shifting between gears.

What causes the P0956 code?

Several factors can contribute to the P0956 code, including:

• Faulty ASM mode switch.
• Wiring issues such as shorts, opens, or corrosion in the circuit.
• Poor connection or damage to the connectors.
• Problems with the transmission control module (TCM) or its programming.
• Low transmission fluid levels or contaminated fluid.
• Mechanical issues within the transmission itself.

How to fix P0956?

To resolve the P0956 fault code, consider the following steps:

• Perform a thorough diagnostic scan to confirm the fault and check for additional trouble codes.
• Inspect the ASM mode switch and wiring for signs of damage or poor connections.
• Test and, if necessary, replace the ASM mode switch.
• Check and top off transmission fluid levels, ensuring fluid is clean and free from contaminants.
• If the issue persists, further evaluate the TCM or consider reprogramming it if it has software issues.
• As a last resort, a complete transmission inspection may be required to identify internal mechanical problems.