Nissan Sunny P1629 Engine Trouble Code
What is Nissan Sunny P1629?
When Nissan Sunny P1629 code appears, first check your gas cap. Pull over safely, ensure it is tight, and inspect for cracks. A loose or damaged gas cap affects fuel-system pressure and emissions. A replacement cap costs about $3–$10. This simple fix can resolve the code and improve fuel economy.
P1629 on the Nissan Sunny
In cold climates, Nissan Sunny vehicles frequently log P1629 during the first winter of ownership. Condensation inside the throttle body creates a temporary short circuit in the position sensor wiring, which clears once the engine warms up — but the fault code remains stored.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Vehicle: | Nissan Sunny |
| Brand: | Nissan |
| Model: | Sunny |
| Code: | P1629 |
P1629 Nissan Sunny Symptoms
Check Engine Light
Illuminated Nissan Sunny dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Nissan Sunny
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Nissan Sunny
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 Sunny P1629
Diagnostic Steps:
Oxygen sensors measure exhaust gas oxygen content to optimise air-fuel ratio. This optimisation improves fuel economy and reduces emissions. Sensors degrade over time and require periodic replacement.
Repair Solution:
VSS concerns may stem from noisy input signals caused by RFI/EMI from ignition wires, charging circuits, or aftermarket equipment. Verify VSS reads 0 mph when transmission is in Park.
Technical Notes:
P1629 DTC specifically relates to camshaft timing. When cam timing is over-retarded, the check-engine light illuminates and this code sets. Verify VCT solenoid operation and check for contamination.
Nissan Sunny P1629 Repair Cost
Replacing the lambda (O2) sensor wiring loom section on the Nissan Sunny costs $90–$160 at a body shop or auto-electrician. This is far cheaper than replacing the sensor itself when the sensor is otherwise functional — always inspect wiring before condemning sensors.
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 Sunny
A frequent misdiagnosis on the Nissan Sunny is replacing the oxygen sensor when P1629 appears, only for the code to return within days. The actual cause is usually an exhaust manifold gasket leak introducing false air before the upstream O2 sensor — a much cheaper fix.
DIY Repair Guide: P1629 on Nissan Sunny
When attempting DIY diagnosis of P1629 on your Nissan Sunny, a smoke machine test is the gold standard for finding vacuum leaks. Rental tools are available from most auto parts stores for $0–$20/day, or you can fabricate a makeshift tester using a hand vacuum pump and soapy water spray.
Preventing P1629 on the Nissan Sunny
Ensure the Nissan Sunny oil cap and dipstick tube seal are airtight. Even a small crank-case vacuum leak can cause the PCM to log P1629 and, over time, allows moisture-laden air to degrade the engine oil faster than the scheduled service interval.
Frequently Asked Questions — Nissan Sunny P1629
A: If your Nissan Sunny is within the factory powertrain warranty period (typically 3–5 years or 60,000–100,000 miles depending on region and generation), P1629 repairs caused by component defects should be covered. Bring your service history to the dealer appointment.