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hypoxia · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

ISX CM870 with intermittent code 595, Turbocharger Speed High. Usually get the CEL coming off of idle at a stop or after descending a hill when power is added. It just illuminates for a second or two then goes away. It didn't illuminate the light for the first bunch of times but I saw it on Insite. I haven't recorded the parameters using Insite but I could if needed.

I checked the plugs, harness (ECM to sensor) and the turbocharger speed sensor; they all check OK. I'm thinking of replacing the turbocharger speed sensor, 4032068. I see some aftermarket sensors for less than $100 or the Cummins part is around $230. Suggestions?

Chamberpains · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

NEVER go aftermarket with critical sensors and parts. You'll pay at least twice the savings in no time when they fail or don't read as they should.

Is this engine demandated (deleted)

hypoxia · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

(10-10-2020 )Chamberpains Wrote: NEVER go aftermarket with critical sensors and parts. You'll pay at least twice the savings in no time when they fail or don't read as they should.

Is this engine demandated (deleted)

Yes by Mommaburt! I figured you'd say OEM parts but I couldn't resist poking the bear with a stick. :) I was wondering if these turbo speed sensors did this often?

Chamberpains · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

I'd monitor the sensor speed with insite or cterm and see what its reading. If its flickering erratically then its probably gonna be the sensor or a wire that you didn't see busted up or corroded. Also check the turbo turbine for excess play or excess soot or damage to make sure its not the root if the problem.

marek4792 · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

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.

Signature620 · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

I'm not very familiar with the CM870 but have a good read of the fault code information. On the CM570, 595 is 'turbo speed data above normal' but generally means the boost is higher than the limits set for that eng speed and fuelling.

It could be actuator related, barometric pressure related, leaking actuator signal hose, etc. Not saying it won't be the speed sensor, but do some digging before you load up the parts cannon.

hypoxia · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

Since it only does it immediately coming off of idle and before the RPMs go up much at all I'll take that advice and record it with Insite. The exhaust side of the turbo feels good, zero lateral movement.

Rawze · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

you also did not mention how much boost it was making... or if you have pressurized up the whole engine to see if there are any boost leaks.

could simply be the speed sensor but like others have said... clogged exhaust,. bad intake air filter, or actuator acting up can cause it too.

and .. if you have the mentality of trying to save money on engine sensors by going aftermarket ... or you can't afford it... ..your in the wrong business!.

hypoxia · 10-10-2020, **(Subject: CM870 Turbocharger Speed Sensor )**

(10-10-2020 )Rawze Wrote: you also did not mention how much boost it was making... or if you have pressurized up the whole engine to see if there are any boost leaks.

could simply be the speed sensor but like others have said... clogged exhaust,. bad intake air filter, or actuator acting up can cause it too.

and .. if you have the mentality of trying to save money on engine sensors by going aftermarket ... or you can't afford it... ..your in the wrong business!.

Since demandate, boost will just hit 32 for a second, normally below 30. Pulls mountain grades OK, two or three MPH slower than before. Have not pressurized it yet. EGT has been good. I think exhaust and intake filter OK. I've been on the road since May & out again in a week but for a short time. I chuckled when I asked about aftermarket parts as I figured what the answer was but I had a stick and couldn't resist poking the bear. :) You guys are great!