Bmw 420 P1629 Engine Trouble Code
What is Bmw 420 P1629?
Bmw 420 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 Bmw 420
For Bmw 420 owners, diagnosing P1629 correctly requires ruling out a faulty camshaft position sensor before replacing more expensive components. The sensor wiring harness on this model runs close to the exhaust manifold and is prone to heat-related insulation damage.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Vehicle: | Bmw 420 |
| Brand: | Bmw |
| Model: | 420 |
| Code: | P1629 |
P1629 Bmw 420 Symptoms
Check Engine Light
Illuminated Bmw 420 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Bmw 420
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Bmw 420
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 420 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:
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 420 P1629 Repair Cost
When P1629 appears on a Bmw 420, 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 Bmw 420
On Bmw 420 vehicles, the turbo boost solenoid and the MAP sensor feed into the same diagnostic path. P1629 caused by a faulty boost solenoid is sometimes charged to the customer as a MAP sensor replacement, doubling unnecessary parts spend.
DIY Repair Guide: P1629 on Bmw 420
For the Bmw 420, an EGR valve inspection is a useful DIY step before spending money on diagnosis. Remove the valve (2–4 bolts depending on generation), inspect for carbon build-up, and use carburettor cleaner and a soft brass brush to clean the valve face and seat.
Preventing P1629 on the Bmw 420
After any fuel system repair on the Bmw 420, 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 — Bmw 420 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.