Repair of the Peugeot 508 HYbrid4 hybrid system at STS Warsaw
PEUGEOT 508
The HYbrid4 system, which combines a 2.0 HDi diesel engine with a starter generator and an electric motor on the rear axle, has become a real engineering showcase for Peugeot. It provides the economy of a diesel engine, additional electric torque during start-up and the ability to drive on electric power for short periods. This architecture is complex and therefore requires flawless precision in terms of settings and maintenance — even a minor error can completely block the engine from starting.
Fault details and diagnostics
The owner of a Peugeot 508 HYbrid4 Berline contacted the STS Electro workshop (Warsaw) with typical symptoms of a hybrid system failure. The display showed the following messages: ‘Check engine’, ‘System malfunction’, ‘Stop - service’.
The car would not start because the hybrid system was blocking the diesel engine. During diagnostics using a scanner, STS specialists saw a large number of errors in the starter-generator: the unit did not see the rotation task, discrepancies in torque and speed were recorded, and the system complained about the lack of correct measurements.
After clearing the errors, the technicians heard a characteristic squeaking of the belt. A few seconds of slippage — and the hybrid system went back into emergency mode, completely blocking the engine start. The reason — the belt was slipping, which meant that the starter-generator could not adequately assess the load, ‘malfunctioned’ and stopped the system.
Repair and restoration of operation
During the inspection, it was found that:
- the belt is new, the letters on it are still white;
- however, it is not properly tensioned;
- the owner reported that the starter-generator had recently been repaired and the belt had been replaced twice — the first one even broke shortly after installation.
STS Electro specialists checked the pulley, rollers and tensioner — all elements were found to be in good working order. After adjusting the tension of the V-belt (6 streams), the starter-generator began to work stably — without slipping, without errors, both when cold and when hot.
Conclusions
In Peugeot hybrids (especially systems with a belt starter-generator), the condition of the drive belt critically affects the operation of the entire hybrid part. The electronics do not have a tension sensor — they only detect load discrepancies and immediately block the engine to prevent damage to the components.
Therefore, even a slight slippage of the belt can cause the hybrid system to shut down completely.
Professional assessment by STS
STS Electro specialists demonstrated the attentiveness and technical depth characteristic of the team: they noticed a detail that others might have overlooked, restored the system to proper working order without unnecessary replacement of components, and returned a fully functional car to its owner.
STS is a workshop where they see more than what the diagnostics show. It is here in Warsaw that French hybrids come back to life.
Similar cases have occurred repeatedly in STS Electro's practice. For Peugeot hybrids with the HYbrid4 system, errors due to incorrect belt tension are a typical problem, especially after intervention by third-party mechanics. The STS team has extensive experience in diagnosing and troubleshooting electric and hybrid vehicles, so even complex French systems are brought back to life quickly, accurately and professionally.
