Comprehensive diagnostic guide for OBD-II code P0780

Based on provided, this guide focuses on a cautious, safety-first diagnostic approach. Note: the exact definition of P0780 is not explicitly provided . The open-source and GitHub entries align P0780 with shifting/gear-related concerns, while NHTSA complaints show real-world transmission-sensor involvement in at least one case. Treat P0780 as a transmission/gear-shift related powertrain code and proceed with a broad but structured diagnostic plan.

1) Code interpretation and scope

• What the sources say
  • OBD-II context: DTCs in the Powertrain category are triggered by the engine/transmission control systems when monitored parameters are out of spec, and the system stores these codes for service and repair.
  • Gear/shift related wording: An open-source entry notes a concept described as "Mau funcionamento das mudanças de marcha" (malfunction of gear shifting), implying P0780-type indications relate to shifting/gear selection systems.
  • Real-world complaints: A verified NHTSA complaint describes transmission-related concerns including a transmission sensor being involved, with initial resolution of a recall, followed by later transmission-related check engine activity and sensor mentions. This illustrates that the transmission/shift sensor area is a plausible source of P0780-like symptoms in at least one real-world case.
• Practical takeaway
  • P0780, in the absence of a single explicit official definition , should be treated as a transmission/gear-shift related powertrain code. The diagnostic approach should cover transmission-range sensor circuits, shift solenoids, valve/body, TCM/PCM control and related wiring.

2) Common symptoms (informational)

• From the user-provided NHTSA complaint: check engine light on shortly after purchase, later symptoms described as a transmission-related sensor issue; a recall repair had been performed prior to the later problem. This emphasizes that symptoms can present as an illuminated MIL with transmission-associated sensor or circuit concerns.
• General symptoms you might observe with P0780-type issues (consistent with shifting/gear-related codes and the cited "gear shift" concept):
  • Inconsistent or harsh/late shifting
  • Transmission not entering expected gear or failing to up/downshift
  • Engine RPM behavior not matching gear (misalignment between commanded gear and actual gear)
  • MIL illumination with related transmission/system codes

3) Probable causes and estimated likelihood (caution on data)

Note: The sources provide limited numeric pattern data. The following probabilities are educated estimates for field troubleshooting, tempered by the NHTSA complaint example and general OBD-II experience. They are not definitive statistical claims from a large data set.

• Transmission Range Sensor (TRS) circuit or TRS itself (sensor misreadings, wiring, connector issues): 30-50%
  • Why: TRS is a primary device that communicates the selected gear to the TCM. Wiring and sensor faults commonly trigger shifting/gear-related codes in many vehicles.
• Shift solenoids and/or valve body issues (solenoid faults, stuck valves, improper control voltages): 15-25%
  • Why: Shifting is hydraulically actuated via valve bodies and solenoids; faults here can produce mis-shifting or improper gear engagement.
• Transmission Control Module (TCM) or PCM/TCM communication/processing fault (calibration, software, faulty ground/power): 10-20%
  • Why: The TCM interprets sensor data and commands solenoids; faults can manifest as false/shifting misbehavior and DTCs.
• Wiring harnesses, grounds, connectors (corrosion, loose pins, pin damage): 10-15%
  • Why: Electrical faults in the TRS circuit, solenoid circuits, or TCM power/ground paths commonly produce intermittent or persistent codes.
• Transmission fluid condition and level (low or dirty fluid) or external contamination affecting hydraulics: 5-10%
  • Why: Hydraulics rely on proper pressure; degraded fluid can cause shifting irregularities and sensor disagreements.
• Mechanical/valve-body wear or internal transmission damage (more severe cases): 5-10%
  • Why: If hydraulic pressure or valve timing is degraded, sensors may report mismatches or shifts may fail.

This diagnostic guide was generated using verified reference data:

• NHTSA Consumer Complaints: 1 real-world reports analyzed
• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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