CM870 Turbocharger Speed Sensor

[marek4792]

What i've noticed on my 870 when mine did that under full load in higher elevation 7500+ feet the turbo rpm would steadily climb to and max out at 120,000 rpm then jump to 150,000+ rpm triggering the turbo speed code. From what I was told by Gearhead and Unilever was that a pre turbo exhaust leak or boost leak can cause the turbo to over compensate making the turbo spin faster than it should. Excessive back pressure can do it too, sticking VG vanes, and/ bad actuator.