P0720 — Output speed sensor circuit erratic
What it means: Output speed sensor circuit erratic.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Inspect sensor air gap
Don't risk it — look up listed providers near you and give them this code when you call.
Listed providers nearest Houston, TX
Closest first. Tell them P0720 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Houston, TX · (832) 377-0578
- 0.0 mi away — based in Houston, TX · (713) 219-9090
- 0.0 mi away — based in Houston, TX · (713) 671-9751
Seen on: Output shaft speed
What P0720 means
Output speed sensor circuit erratic. Common causes: Sensor|Tone wheel|Air gap|Wire rub.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Sensor
- Tone wheel
- Air gap
- Wire rub
First moves (roadside)
- Inspect sensor air gap
- Tone wheel condition
FAQ
Output speed sensor circuit erratic. Common causes: Sensor|Tone wheel|Air gap|Wire rub.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Sensor. Other possibilities include Tone wheel; Air gap; Wire rub.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside P0720, or share the same subsystem.
- Main shaft speed erratic (SPN 160 FMI 2)
- Input shaft speed erratic (SPN 161 FMI 2)
- Transmission output retarder speed erratic (SPN 162 FMI 2)
- Trans oil temperature very high (SPN 177 FMI 0)
- Trans oil temperature voltage high (SPN 177 FMI 3)
- Trans oil temperature voltage low (SPN 177 FMI 4)
- Engine speed signal abnormal update rate (SPN 190 FMI 9)
- Transmission output shaft speed erratic (SPN 191 FMI 2)
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.