Nissan R391 P1629 Engine Trouble Code
What is Nissan R391 P1629?
Nissan R391 P1629 indicates potential catalytic converter failure. If completely failed, your vehicle may not run properly and fuel economy will suffer significantly. Average replacement cost is $2,000–$2,140. This repair requires professional service and should not be delayed.
P1629 on the Nissan R391
Service bulletins for the Nissan R391 specifically mention P1629 as a symptom of failed purge solenoid valves in the EVAP system. The solenoid body on this platform degrades in high-humidity environments and should be inspected whenever this code appears.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Vehicle: | Nissan R391 |
| Brand: | Nissan |
| Model: | R391 |
| Code: | P1629 |
P1629 Nissan R391 Symptoms
Check Engine Light
Illuminated Nissan R391 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Nissan R391
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Nissan R391
Increased Emissions
Failed emissions test due to P1629
P1629 Code Structure
Understanding what each digit means in the P1629 powertrain trouble code:
| P | 1 | 6 | 2 | 9 |
|---|---|---|---|---|
| Powertrain Code | Fuel And Air Metering | Fuel Temperature Sensor B Circuit Range/Performance | Turbocharger Boost Sensor A Circuit Low | Reverse Input Circuit |
How to Fix Nissan R391 P1629
Diagnostic Steps:
The catalytic converter has oxygen sensors before and after it. When warm and in closed-loop mode, the upstream O2 sensor reading should fluctuate, while downstream should remain steady.
Repair Solution:
A/C pressure sensor monitors refrigerant pressure changes. DTC sets when pressure change falls outside calibration. Verify A/C system function, refrigerant charge, and electrical connections.
Technical Notes:
For P1629, verify VCT solenoid operation. Look for stuck or sticking valves caused by contamination. Consult vehicle-specific repair manual for proper component testing procedures.
Nissan R391 P1629 Repair Cost
When P1629 appears on a Nissan R391, a camshaft position sensor swap costs $140–$260 all-in. This is one of the more affordable sensors on this platform. If the wiring harness is also damaged, add $60–$90 for harness repair or section replacement.
P1629 Description
P1629 engine trouble code is related to Reverse Input Circuit.
Main Cause
The primary reason for P1629 OBD-II Engine Trouble Code is: Fuel Temperature Sensor B Circuit Range/Performance.
Common P1629 Misdiagnosis on the Nissan R391
The Nissan R391 purge valve for the EVAP system is located in an area prone to heat damage. It is often overlooked in favour of replacing the carbon canister ($120–$200) when the valve itself ($25–$50) is the failed component for P1629.
DIY Repair Guide: P1629 on Nissan R391
After any repair that involved disconnecting the battery on the Nissan R391, the power window, steering angle sensor, and transmission adaptive values all require a reset drive cycle. Skipping this can cause false fault codes — including P1629 — for the first two to three start cycles.
Preventing P1629 on the Nissan R391
After any fuel system repair on the Nissan R391, always perform a fuel-trim reset and adaptation drive. Skipping this step leaves the ECU operating on pre-repair learned values, which can generate false P1629 alerts for weeks after the fix.
Frequently Asked Questions — Nissan R391 P1629
A: Simple fixes like a purge valve or gas cap replacement take under an hour. Sensor replacements typically require 1–2 hours of shop time. More involved repairs like VVT actuators or catalytic converters may require a full day or more.