P0340 Howo — camshaft position sensor circuit (CMP)

Fault codes / P0340

Without FMI this is not a full diagnosis if the scanner showed SPN 4201 only. SAE P0340 is Camshaft Position Sensor A Circuit. Weichai table: SPN 4201 FMI 12 / P00EC = no cam signal; FMI 14 / P00ED = signal deviation. Not P0335 (crank). No OEM in this card.

Which trucks see it

Howo, Shacman, Sitrak, Weichai WP10–WP13, WD615. Type P0340, P00EC or 4201/12 as on the screen.

Symptoms

• long crank, rough idle
• MIL, sometimes with P0335
• oily plug at the valve cover

Likely causes

• SAE: CMP circuit.
• Weichai: FMI splits no-signal vs deviation.
• Oily plug / loom. Timing marks only after both sensors are alive.

What to check

1. Read FMI.
2. Power/ground/signal, CKP vs CMP on a scope.
3. Then marks. No invented OEM.

Can you keep driving

If it runs, limp to a shop. No-start with P0335 — tow. Home form: P0340 or 4201/12.

Look up the code in the service

Other codes

• P0087 — low common-rail pressure
• P0088 — high common-rail pressure
• P1011 — HP pump metering valve fault
• P0093 — large fuel leak / CAN trap — FMI needed
• P0193 — rail pressure sensor high signal
• P0299 — boost below target
• P2263 — turbo / boost performance
• P2563 — VGT position sensor — range / performance
• P0335 — crankshaft sensor no signal
• P0401 — EGR insufficient flow
• U0100 — lost communication with engine ECU
• U0101 — lost communication with TCM
• U0155 — lost communication with instrument cluster
• P0562 — system voltage low
• P0201 — cylinder 1 injector circuit
• P0480 — fan control circuit
• P0217 — engine overheat
• P0116 — water in fuel (Weichai table) / not always coolant SAE
• P2509 — intermittent ECM power (no OEM in DB)
• SPN 2898 — without FMI — not a diagnosis (config / Weichai grid)
• SPN 729 — intake heater — FMI needed