Description
Injection Control Unit SIEMENS SID 803A. It is from Citroën C5 II 2.0 HDi (RHR).
This Siemens SID 803A engine control unit (ECU) is an original-style electronic control module used on PSA Group diesel engines. It manages injection timing, fuel metering, turbo boost and key engine management functions to ensure reliable performance and emissions control. The unit is commonly fitted to Citroën C5 II 2.0 HDi (RHR) and equivalent PSA applications and is frequently searched for by its product codes—making it easy to find in parts databases and search engines.
Designed for professional mechanics and experienced DIYers, this ECU is a direct replacement option for vehicles showing symptoms such as engine won’t start, intermittent stalling, rough idle, loss of power, or persistent engine warning lights. When sourcing a replacement, using the exact product codes listed below improves the chance of a correct match and faster diagnosis.
Technical information
- Manufacturer: Siemens
- Model: SID 803A; Citroën C5 II 2.0 HDi (RHR)
- Product Codes: 9662273180, 9655534080, 5WS40258G-T, 1940ZE, 1940ZF
- Additional Numbers: 1942X8, 1942Y0, 194003, 1942X
Installation recommendation
Before starting work disconnect the negative battery terminal to avoid short circuits and protect vehicle electronics. Remove any trim or covers to access the ECU mounting location, unplug electrical connectors carefully using the locking tabs, and unbolt the control unit from its bracket. Fit the replacement unit in the reverse order, ensuring connectors are fully seated and mounting points are secured. After installation, perform a full diagnostic scan and clear any stored fault codes. Be aware that many modern ECUs require coding or programming to the vehicle immobiliser and engine management system; use a professional diagnostic tool or workshop that can perform ECU programming if required.
Why this part most commonly fails
Failures are usually caused by environmental and electrical stress rather than routine wear. Common causes include water ingress or moisture-related corrosion, thermal cycling and overheating, voltage spikes or poor battery/charging system condition, and degraded solder joints or internal electronic components on high-mileage units. Symptoms typically include intermittent faults, engine management warning lights, loss of communication with diagnostic tools, rough running or no-start conditions. Addressing underlying issues such as a weak battery, poor ground connections, or water leaks will reduce the risk of repeat failures.
