JLG ES series scissor lifts (1930ES, 2030ES, 2630ES, 2646ES, 3246ES)
JLG error code 312 — CONTACTOR DRIVER PERMANENTLY OFF
Message on the display: CONTACTOR DRIVER PERMANENTLY OFF
blocking fault
The power modules line contactor drive circuitry failed to energize when requested. Drive, steer and lift up prevented.
Description from the JLG service manual, in the original wording.
Possible causes
The manual does not list the causes for this code: the service technician establishes them during diagnosis of the machine.
Checks from the manual
- Check continuity between contactor connector pin 1 and ground board socket J1-19.
- Contactor solenoid resistance should measure about 52 Ohms.
- Check continuity between contactor connector pin 2 and power module connector socket 8.
- Replace power module.
What service does
A qualified service technician reads the code with the manufacturer's diagnostic tools, finds the cause, clears the code and carries out a function test.
Source: JLG Service and Maintenance Manual, ES series (Diagnostic Trouble Codes section).
The descriptions are quoted from the manufacturer's service documentation and are for guidance only. Clearing codes, calibrations and repairs are carried out by a qualified service technician according to the manual for the specific serial number. A machine with an active blocking code must not be used until the cause has been removed.
Does code 312 not go away?
RK Rental services JLG lifts at our workshop or on site at the customer's premises (construction site, factory, warehouse). We read the code, remove the cause and select the parts by serial number.