Nissan Altima P0845 Transmission Fluid Pressure Sensor B Pri Pressure Sensor

Description

The TFPS B plays a pivotal role in detecting primary pressure in the Continuous Variable Transmission (CVT) system, relaying this vital information to the Transmission Control Module (TCM). The diagnostic trouble code (DTC) P0845 indicates potential issues with this sensor, prompting the need for a comprehensive diagnosis.

Troubleshooting Process

DTC Logic

The diagnostic process begins with the Detection Logic of the DTC. Following a Confirmation Procedure, the system checks for the presence of the specific code “P0845 TR PRS SENS/B CIRC.”

Diagnosis Procedure

  1. Check Input Signal
    • Start the engine.
    • Examine voltage between TCM harness connector F16 terminal 14 and ground.
  2. Check Sensor Power and Sensor Ground
    • With the ignition switch on, assess voltage between TCM harness connector F16 terminal 25 and 26.
  3. Check Harness Between TCM and CVT Unit (Part 1)
    • Turn off the ignition and inspect continuity between TCM harness connector F16 terminal 14 and CVT unit harness connector F46 terminal 25.
  4. Check Harness Between TCM and CVT Unit (Part 2)
    • Evaluate continuity between TCM harness connector F16 terminal 14 and ground.
  5. Check Harness Between TCM and CVT Unit (Sensor Power and Sensor Ground) (Part 1)
    • Turn off the ignition and assess continuity between TCM harness connector F16 terminal 25, 26 and CVT unit harness connector F46 terminal 19, 20.
  6. Check Harness Between TCM and CVT Unit (Sensor Power and Sensor Ground) (Part 2)
    • Examine continuity between TCM harness connector F16 terminal 25, 26 and ground.
  7. Check TCM
    • If needed, replace the TCM following specified procedures.
  8. Detect Malfunctioning Items
    • Inspect TCM connector pin terminals for damage or loose connection.

Technical Description of OBD-II Trouble Code

The article transitions into a technical perspective, elucidating the OBD-II Trouble Code P0845 and its significance. It describes the circuit for the Transmission Fluid Pressure Sensor/Switch “B” and its application across various vehicle brands, including Nissan.

Code Severity & Symptoms

Understanding the severity of the code and associated symptoms is imperative. The severity varies based on the circuit affected. Symptoms may include the Malfunction Indicator Light being illuminated, changes in shift quality, or the vehicle starting off in 2nd or 3rd gear (limp-in mode).

Causes

The causes of P0845 are outlined, primarily pointing towards electrical circuit issues or potential internal mechanical problems within the transmission. The article stresses the importance of not overlooking mechanical aspects during troubleshooting.

Diagnostic and Repair Procedures

The final section provides guidance on diagnostic and repair procedures. It advocates checking technical service bulletins (TSB) for known issues and recommends a systematic approach to diagnosis. The article emphasizes visual inspection of connectors and wiring, and if necessary, employing a scan tool for code clearance.

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