Anyone experience a loss of boost ONLY in 5th and 6th gear at highway speeds? Had faults for IAT and ECT sensors, replaced and no more codes but still acting up. 1st-4th gear are fine but the boost needle stays dead in 5th and 6th and has no power. Very frustrating, please help.
No Boost In 5th and 6th only
- Thread starter TOM BSKI
- Start date
PeteK
GT Owner
That’s weird. As far as I know, there are no sensors on the transmission that signal the ECU what gear you’re in. Boost should only respond to your right foot. Are you sure it’s not related to RPM instead of gear? Do some testing at the same RPM in all gears.
That's correct, Pete. The GT hasn't a clue what gear it's in so something else is going on here. OP - are you shifting from 4-5 under full boost (in 4th)? If so, what if you try just rowing up through the gears into 5th and then going WOT there? Any differences?
You might try to zip-tie / tape / bailing wire a GoPro or similar in the engine compartment and focus on the bypass solenoid. It would be interesting to see if this is the culprit - but then the harder part is in trying to determine why. So, while recording, it would be interesting to capture different scenarios in order to narrow down how/why this is happening.