P0259
Injection Pump Fuel Metering Control B High
When a vehicle powertrain module registers the fault code P0259, it points directly to an internal system malfunction identified as "Injection Pump Fuel Metering Control B High". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
The diagnostic trouble code P0259 indicates an active fault in the injection pump fuel metering control b high circuit or component. In practice, this fault causes rich fuel mixture, black exhaust smoke. Stop driving as soon as it is safe to do so. This fault can lead to expensive secondary damage if left unaddressed.
Symptoms
Rich fuel mixture, black exhaust smoke
Common Causes
- Short to battery voltage
- Disconnected plug
- Internally failed regulator
- Failed PCM
How to Fix
- 1 Repair short to voltage
- 2 Secure electrical connector
- 3 Replace metering valve/regulator
- 4 Replace PCM
Technical Explanation
The ECM detects code P0259 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including short to battery voltage — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
Module replacement should always be the last resort for P0259 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Regulator replacement: 200 - 500