Bmw 120 P1629 Engine Trouble Code
What is Bmw 120 P1629?
Bmw 120 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 Bmw 120
The Bmw 120 is particularly susceptible to P1629 faults when the engine management unit receives conflicting sensor data. Owners report that P1629 on Bmw 120 most commonly surfaces after 60,000 miles, especially when routine service intervals have been missed.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Vehicle: | Bmw 120 |
| Brand: | Bmw |
| Model: | 120 |
| Code: | P1629 |
P1629 Bmw 120 Symptoms
Check Engine Light
Illuminated Bmw 120 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Bmw 120
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Bmw 120
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 Bmw 120 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:
Power steering pressure switch monitors system operation. If pressure changes are not detected after calibrated speed transitions, this DTC sets. Verify PSP switch operation and check for circuit opens or shorts.
Technical Notes:
P1629 DTCs can be triggered by upstream issues. For example, a dirty MAF sensor may cause incorrect fuel-trim adjustments, leading oxygen sensors to report mixture problems. Address root causes first.
Bmw 120 P1629 Repair Cost
Addressing P1629 on your Bmw 120 typically involves: dealer diagnostic fee $95–$150, oxygen sensor replacement $180–$320 (parts + labour), or catalytic converter replacement $1,800–$2,400 if damage has progressed. Independent specialist garages often charge 20–30% less than franchised dealers for identical work.
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 Bmw 120
On the Bmw 120, the EGR cooler is sometimes replaced for P1629 when the EGR valve position sensor is at fault. The two components share a fault pathway in older scan tools that do not display live EGR valve position data.
DIY Repair Guide: P1629 on Bmw 120
The Bmw 120 EVAP purge solenoid valve is accessible without lifting the vehicle — it is mounted on the intake manifold and secured by a single bolt and a vacuum hose clip. DIY replacement is rated 1/5 difficulty and takes approximately 20 minutes.
Preventing P1629 on the Bmw 120
Keeping the Bmw 120 battery in good health — testing specific gravity annually and replacing at first sign of degradation — protects the ECU voltage supply. Voltage drops during cranking cause sensor reading spikes that can spuriously store P1629.
Frequently Asked Questions — Bmw 120 P1629
A: It depends on the severity. If the check-engine light is steady, it is generally safe to drive to a workshop within the next few days. If the light is flashing, pull over safely as soon as possible — a flashing light indicates an active misfire that can cause expensive catalytic converter damage within minutes.