Nissan Mid4 P1629 Engine Trouble Code
What is Nissan Mid4 P1629?
Nissan Mid4 P1629 code can indicate a faulty oxygen sensor, which may eventually damage the catalytic converter (repair cost: $2,000–$2,200). Professional diagnosis costs around $200–$210. Oxygen sensors are often straightforward to replace — check your owner's manual for location and instructions. This issue should be addressed promptly to prevent further damage.
P1629 on the Nissan Mid4
On the Nissan Mid4, a secondary air injection pump that has seized due to moisture ingress is a common trigger for P1629. The fault is usually only present on cold starts and clears itself after two to three warm-up cycles, making it easy to overlook.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Vehicle: | Nissan Mid4 |
| Brand: | Nissan |
| Model: | Mid4 |
| Code: | P1629 |
P1629 Nissan Mid4 Symptoms
Check Engine Light
Illuminated Nissan Mid4 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Nissan Mid4
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Nissan Mid4
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 Mid4 P1629
Diagnostic Steps:
Regarding P1629, carefully inspect the wire harness near the intake manifold bracket, best accessed from below near the oil filter. Look for chafing, pinching, or damaged insulation.
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 Mid4 P1629 Repair Cost
For Nissan Mid4 owners, budget the following for a P1629 repair: EGR valve cleaning $80–$120 or replacement $250–$450, intake manifold gasket $120–$200, and a post-repair reset and road test. Total: $350–$650 at an independent garage.
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 Mid4
Fuel injector replacement is over-prescribed on the Nissan Mid4 for P1629 when the actual fault is a weak fuel pump. Low fuel rail pressure causes lean misfire that looks identical to injector failure in static scan data without a live fuel pressure test.
DIY Repair Guide: P1629 on Nissan Mid4
The throttle body on the Nissan Mid4 can be cleaned without full removal. Use a clean rag and throttle body cleaner spray with the engine off and cool. After cleaning, an idle relearn is mandatory: disconnect the battery for 10 minutes, reconnect, and allow the engine to idle for 10 minutes undisturbed.
Preventing P1629 on the Nissan Mid4
Scheduled inspection of the Nissan Mid4 air filter every 15,000 miles can prevent the intake restriction that leads to P1629. A blocked filter forces the engine to run rich, stressing the catalytic converter and ultimately storing fault codes.
Frequently Asked Questions — Nissan Mid4 P1629
A: If your Nissan Mid4 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.