Cummins Fault Code 121: Engine Speed/Position Sensor Circuit - lost one of two signals from the magnetic pickup sensor

Code details

Manufacturer

Cummins

Applies to

Cummins QS-series electronic engines

Fault code

121

J1939 SPN

190

FMI

10 — Abnormal rate of change

J1587 PID / SID

P190

Engine models

QSC, QSL9, QSM11, QSX15, QSK19, QSK23, QST30

QSK45/60/78 severity level

QSK45: 2 • QSK60: 2 • QSK78: 2

What to do next

• Read active and inactive codes with the OEM service tool and note the occurrence count.
• FMI 10 tells the shop the type of failure to test for: abnormal rate of change.
• Have a heavy-duty diesel technician confirm the fault against the engine or chassis service manual before replacing parts.

Related fault codes

• Cummins Fault Code 115 — Engine Speed/Position Sensor Circuit - lost both of two signals from the magnetic pickup sensor
• Cummins Fault Code 234 — Engine Speed High – Critical
• PACCAR Fault Code P0017 — Crankshaft Speed Signal – Not Corresponding With Engine Position
• PACCAR Fault Code P0219 — Engine Speed – Data Valid But Too High
• PACCAR Fault Code P0335 — Crankshaft Speed Signal – Disturbed or No Signal During Engine Operation
• PACCAR Fault Code P1335 — Crankshaft Speed Signal – Disturbed or NO Signal During Engine Start
• PACCAR Fault Code P1336 — Crankshaft Speed Signal – Out of Range During Engine Start
• International Fault Code SPN 190 FMI 0 — Engine Overspeed – Most Severe Level