The P1734 diagnostic trouble code (DTC) for Nissan vehicles indicates a “Power Steering Pressure (PSP) Switch Signal Malfunction”. This code is triggered when the Powertrain Control Module (PCM) detects an unexpected signal from the power steering pressure switch, specifically related to vehicle speed transitions. Let’s delve deeper into understanding this code, its potential causes, and troubleshooting steps.
The PCM in your Nissan is designed to monitor various systems, including the power steering. It counts how many times your vehicle’s speed transitions from 0 mph to a certain calibrated speed. After a specific number of these transitions, the PCM expects the PSP switch signal to have changed its state. The P1734 code is set when this expected transition in the PSP switch signal is not detected by the PCM.
Several factors can lead to a P1734 code. Here are some common culprits:
- Faulty PSP Switch: The power steering pressure switch itself may be malfunctioning. It could be damaged, internally shorted, or failing to send the correct signal to the PCM.
- PSP Switch/Shorting Bar Damage: Physical damage to the PSP switch or its associated shorting bar can disrupt the signal.
- SIG RTN Circuit Open: An open circuit in the Signal Return (SIG RTN) circuit can prevent the PSP switch signal from reaching the PCM.
- PSP Circuit Open or Shorted to SIGRTN: The PSP circuit could be open, meaning a break in the wiring, or shorted to the SIGRTN circuit, causing signal interference.
- PCM Damage: In rare cases, damage to the PCM itself could be the cause, although this is less frequent than issues with the switch or wiring.
- Vehicle Towed with Engine Running: As noted in the original context, towing the vehicle with the engine running could potentially trigger this code under certain conditions, especially if power steering service was performed and the DTC was not properly cleared afterwards.
- Power Steering Hydraulic Concerns: While not a direct cause of the P1734 code itself, underlying hydraulic issues in the power steering system could indirectly affect the PSP switch readings or system behavior, potentially contributing to the code being set.
To diagnose the P1734 code, consider these steps:
- Check for Recent Service or Towing: Inquire if the vehicle was recently towed or if any power steering service was performed. This context can be helpful in narrowing down potential causes.
- Observe PSP V PID: Use a scan tool to observe the Power Steering Pressure Voltage (PSP V) Parameter Identification (PID). Monitor this PID while physically checking and wiggling the wires connected to the PSP switch to identify any intermittent issues in the wiring.
- Inspect PSP Switch and Wiring: Visually inspect the PSP switch for any damage and carefully examine the wiring harness and connectors for signs of damage, corrosion, or loose connections.
It’s important to note that while the original text mentions “P0174 OBDII Repair”, this code is related to lean fuel conditions (System Too Lean Bank 2) and is not directly related to the P1734 code or power steering system. The inclusion of P0174 information in the original text seems unrelated and potentially misleading in the context of diagnosing a P1734 code.
In summary, the Nissan P1734 code signals a malfunction in the power steering pressure switch signal, often linked to wiring problems or a faulty switch itself. Proper diagnosis involves checking the switch, wiring, and using a scan tool to monitor the PSP sensor readings. Addressing this code promptly is important to ensure the power steering system is functioning correctly and the vehicle is operating safely.
