Weichai sits on Howo, Shacman, Sitrak and some buses. Bosch common-rail: rail, pressure sensor, metering valve on the HP pump, CKP at the flywheel, CMP by the filter or pump. The scanner often shows SAE (P0xxx) plus an internal Weichai code — both can be typed into ChinaDiag.
WP10, WP12 and the rail
WP10/WP12 on the road most often give low fuel pressure, a rail-sensor fault and “no comms” after a chafed harness. WP13 on tractors is the same hardware plus intake sensors. Do not mix internal Weichai P-codes with SAE: the service splits them in the database so the wrong OEM is not suggested.
How to use it
On the home page set the truck and WP10/WP12/WP13, type a code or send a photo. You get field-frequency causes, simple-to-hard steps, and a part number only if it is confirmed in the database.