Citroen 5cv P1629 Engine Trouble Code
What is Citroen 5cv P1629?
When Citroen 5cv 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 Citroen 5cv
In cold climates, Citroen 5cv 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: | Citroen 5cv |
| Brand: | Citroen |
| Model: | 5cv |
| Code: | P1629 |
P1629 Citroen 5cv Symptoms
Check Engine Light
Illuminated Citroen 5cv dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Citroen 5cv
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Citroen 5cv
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 Citroen 5cv 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.
Citroen 5cv P1629 Repair Cost
Ground circuit repairs on the Citroen 5cv — a common cause of P1629 — are labour-intensive but parts are cheap. Expect 1.5–2.5 hours of labour ($120–$200) to clean, treat, and re-torque all engine and transmission ground straps. This is excellent value given how often it resolves persistent fault codes.
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 Citroen 5cv
The Citroen 5cv is frequently taken to workshops for a P1629 fault where the technician replaces the throttle position sensor (TPS). In a significant proportion of cases, the root cause is a loose or cracked vacuum hose downstream of the throttle body that should have been found in a basic visual inspection.
DIY Repair Guide: P1629 on Citroen 5cv
For the Citroen 5cv, 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 Citroen 5cv
The Citroen 5cv benefits from an intake manifold decarbonisation at 50,000-mile intervals when direct injection is fitted. Carbon build-up on intake valve stems restricts airflow and creates the lean conditions that trigger P1629.
Frequently Asked Questions — Citroen 5cv P1629
A: If your Citroen 5cv 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.