A 2018 Citroen C4 Cactus arrived in a Swedish workshop with a simple ticket stating the car would not start. The scanner pulled just two codes, P0340 and P1632, creating a diagnostic scenario where replacing the most obvious component would have been a waste of time. When a vehicle will crank but not start and presents a camshaft position code, it is tempting to order a new sensor immediately. The data from our platform tells a different story.
The Voltage Stability Problem
Our engine ranked a power supply or grounding issue to the engine control unit and sensors as the most likely cause, at 90 percent probability. This specific 1.2i EB2ADT engine is highly sensitive to voltage stability.
The fault codes P0340, which indicates a camshaft position sensor circuit issue, and P1632, pointing to the smart generator or module voltage, frequently appear together when a ground point or power supply is compromised. If the ECU detects voltage outside its expected range, it can fail to process the synchronization signals from the camshaft position sensor. This lack of phase synchronization is what prevents the engine from starting.
For this cause, the diagnostic path requires checking the battery voltage specifically during a cranking attempt. Technicians also need to check the main ground points for the chassis and engine for corrosion and ensure they are tightened correctly. Low battery voltage or a weak starter motor can trigger the camshaft code on their own.
Sensor and Circuit Integrity
If the primary voltage and grounds test perfectly, the focus shifts to the camshaft position sensor itself, which our data ranked at a 70 percent probability of being the root cause. The sensor monitors the camshaft position relative to the crankshaft, and the ECU needs this data to control ignition timing and fuel injection. An internal failure from age or heat will stop the signal.
At a 60 percent probability, the fault lies in the wiring harness or the connectors. The P0340 is a circuit code. On the 1.2 PureTech engine, the wiring harness for this sensor runs close to heat-sensitive areas on the cylinder head. This routing increases the risk of brittle insulation or thermal damage. The required tests here are a visual inspection of the harness and a continuity test of the sensor circuit, alongside checking the voltage supply and signal during cranking.
LIN-Bus Communication
The final high-severity cause, ranked at 50 percent, involves the smart alternator and its LIN-bus communication. The P1632 code specifically flags this circuit. On the EB2 engine series, the ECU uses the LIN-bus to communicate with the alternator and calculate electrical load.
If this communication drops, or if the alternator delivers unstable voltage, the ECU can enter a default mode that actively prevents fuel injection and starting. This unstable voltage cascades, affecting the camshaft position sensor's function and triggering the P0340 code as a secondary symptom. The suggested tests are measuring the alternator output voltage and checking the LIN-bus signal directly at the alternator.
Rethinking the Fault Code Sequence
Diagnosing modern electrical systems requires looking at how multiple codes interact rather than treating them as isolated failures. If you see a camshaft code alongside a voltage code on an EB2 engine, check your grounds and cranking voltage before touching the sensor circuit. Let me know if you see this same pattern in your bays.
Reference pages for the codes in this article
- P0340, what we measure for this code across real diagnostics