Brendon Hartley is poised to start the French Grand Prix from the back of the grid after Honda confirmed it had to change all six components on his Formula 1 power unit following an issue during practice on Friday.

Toro Rosso's Hartley was sidelined by an issue in the final 10 minutes at FP2 at Paul Ricard, with the team moving quickly to investigate the issue.

Honda confirmed via Twitter on Saturday ahead of final F1 practice that it had been forced to change all six components on Hartley's power unit, with a penalty sending him to the back of the grid set to be confirmed by the FIA later today.

The power unit will be the updated-spec that made its debut in Canada, where Hartley qualified 12th before crashing out on the first lap following a clash with Lance Stroll.

The penalty comes as the latest setback for Hartley during a tough debut full season that has seen him score just one point through the first seven races, recording a finish of 10th in Baku.

The New Zealander's set was thought to be at risk, with Toro Rosso enquiring about the availability of McLaren junior Lance Stroll, but a lack of alternatives for the team combined with an improvement in performance has eased some of the pressure on Hartley.

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