Can I use the "A" actuator as a reference for testing?

Yes, and it is the most useful thing available on this code — with one condition. If both positions take the same part, the healthy "A" actuator gives you a known-good component sitting on the same engine at the same temperature, which is a better reference for coil resistance than any generic chart value that may not apply to your pump variant. The same applies to inspecting the connectors side by side, where corrosion and terminal spread become obvious by comparison. The condition is that you confirm the two positions actually use the same part first, because some platforms fit different components in "A" and "B", and comparing a reading against the wrong reference is worse than having no reference.

Should I swap the two actuators to see if the fault moves?

No, unless you have confirmed the part numbers match. On many circuits swapping is a sensible test, but here it carries a real risk: some platforms fit different components in the "A" and "B" positions, and installing the wrong one gives you an induced fault stacked on top of the original with no clean way to separate them. You can get the same information without that risk. Measure both coils' resistance, compare connector condition and terminal tension, and command each actuator with a scan tool while watching the circuit. That tells you what a swap would tell you, without disturbing a component that is currently working.

Does circuit low mean a short or an open?

It can be either, and the code cannot tell you which. A short to ground drains current away from the load so the monitored voltage collapses. An open circuit means voltage never returns through the load at all, and the module's internal pull-down leaves the input near ground. Both read low. Rather than guessing, run the same five checks in order every time — fuse and feed, connector, coil resistance, short to ground with the actuator unplugged, and end-to-end continuity — and whichever fault exists will surface. Trying to reason your way to one answer before testing usually costs more time than simply working the list.

Why is the "B" harness more likely to be damaged?

Because of where it has to go. The second metering channel is generally the less accessible one — a rear-mounted pump, the far bank, or a position behind intake plumbing — so its harness runs longer and takes a more convoluted route to get there. A longer route means more brackets to chafe against and more clamps to be pinched under, and the routing frequently passes closer to exhaust components, where heat hardens insulation until it cracks with engine movement. Look for the two distinct signatures: chafe appears as shiny or flattened areas on the insulation, while heat damage appears as stiff, dark, brittle sections that feel noticeably different from healthy wire when flexed.

OBD-II trouble code

P0258: Injection Pump Fuel Metering Control "B" Low (Cam/Rotor/Injector)

Circuit low on the second metering channel. The useful advantage here is that the healthy "A" channel is sitting on the same engine — which gives you a known-good reference for coil resistance, connector condition, and commanded behaviour that no generic specification chart can match.

High severityPowertrainFuel & AirDo not drive

Quick facts

System: Powertrain
Category: Fuel & Air
Severity: High severity
Drivable: No — stop driving until repaired
Repair cost range: $90 – $1,600
DIY difficulty: Advanced DIY

What does P0258 mean?

P0258 is the circuit-low member of the injection pump metering control "B" family and the direct mirror of P0253. The module drove the second channel's metering actuator circuit, measured what came back, and found the voltage below the acceptable window. This is an electrical finding, which separates it cleanly from P0257 — where P0257 says the circuit is fine but the fuel quantity is wrong, P0258 says the module cannot establish a trustworthy electrical connection to the actuator at all.

As with the "A" circuit-low code, two quite different physical faults produce a low reading and they look identical from the module's side. A short to ground gives current an unintended path away from the load and the monitored voltage collapses. An open circuit — a broken wire, a corroded terminal, an open coil — means the voltage never returns through the load, and the module's internal pull-down leaves the input near ground. Because the code cannot distinguish them, the efficient method is a fixed sequence rather than a guess: fuse and power feed, connector condition, actuator coil resistance, a check for a short to ground with the actuator unplugged, and end-to-end continuity of the control wire. Whichever fault exists surfaces from that list without your having to pick a theory first.

What this code offers that P0253 does not is a same-engine reference. There is a second metering actuator on this engine, it is not the one that coded, and where the two positions use the same part it gives you something better than a specification chart: a known-good component operating in the same conditions. Measure the "A" actuator's coil resistance and you have the real-world value for that part on that engine at that temperature, which is a far more useful comparison than a generic figure that may not even apply to your pump variant. The same applies to connector inspection — comparing the two connectors side by side makes corrosion, terminal spread, and seal damage obvious in a way that examining one in isolation does not.

One caveat on that reference: confirm the two positions actually take the same part before drawing conclusions from a resistance comparison, because some platforms fit different components in the "A" and "B" positions. And do not extend the comparison into swapping the two actuators to see whether the fault follows. It sounds efficient, but on a platform where the positions differ, installing the wrong part creates an induced fault stacked on top of the real one with no clean way to separate them. Compare by measurement, not by relocation.

The physical argument specific to the "B" circuit is about where its harness runs. The second metering channel is generally the less accessible one — a rear-mounted pump, a far bank, or a position behind intake plumbing — which means its harness usually runs longer, takes a more convoluted route, and passes closer to exhaust components on the way. Longer routes mean more brackets to chafe against and more clamps to be pinched under. Proximity to the exhaust means heat-hardened insulation that cracks with engine movement. Those are the two damage patterns to look for, and they have distinct appearances: chafe shows up as shiny or flattened areas on the insulation, while heat damage shows up as stiff, dark, brittle sections that feel different from healthy wire when you flex them.

If P0253 is stored alongside P0258, do not condemn two actuators. Two circuits failing the same way at the same time points at something shared — a power feed, a relay, a ground point, a connector both circuits pass through. Find the shared element and one repair clears both codes.

The consequence for the vehicle is the family's usual and it is not gentle. Losing control of fuel metering means most systems default to minimum fuel or cut fuel entirely, so expect hard starting, a no-start, or an abrupt stall. On a two-pump engine the symptom may present as severe imbalance and shaking rather than a clean shutdown, but the outcome is the same: this is a vehicle to get diagnosed, not one to keep driving.

Common causes

Corroded connector at the second metering actuator — often the less-inspected of the two positions
Control wire shorted to ground through chafed insulation along a long, awkwardly routed harness
Open circuit in the control or feed wire from vibration fatigue or a pulled terminal
Heat-hardened, cracked insulation where the "B" harness passes near exhaust components
Blown fuse or failed relay in the "B" actuator's power feed
Open winding inside the "B" metering actuator coil
Internally shorted actuator coil pulling the circuit down
Spread or backed-out terminal losing contact under vibration
Water intrusion into a low-mounted connector from road spray or pressure washing
Poor or corroded ground on the second channel
Shared power feed or ground fault, which normally sets P0253 alongside this code
PCM or pump driver fault, rare and diagnosed only after everything else checks out

Symptoms

Check engine light with P0258 stored
No-start, or extended cranking before the engine catches
Engine starts and stalls almost immediately
Sudden stalling while driving
Severe power loss or a hard fuelling limit
Heavy rough running and shaking from bank imbalance on a two-pump engine
Black or grey exhaust smoke
Loss of power steering assist and vacuum brake assist if the engine stalls while moving
Fault appears or clears with engine temperature, vibration, or road surface
"B" actuator showing no response to scan tool commands while "A" responds normally

Diagnostic steps

1.Confirm which code you have. P0258 is circuit low and P0259 is circuit high, and the two call for almost entirely different tests.
2.Record all stored codes. P0253 alongside this one points at a shared power feed, relay, or ground rather than at two failed actuators.
3.Identify from service data which physical component your manufacturer calls the "B" metering control, and confirm whether the "A" and "B" positions use the same part.
4.Check the "B" actuator's fuse and power feed first. It is the fastest check and it eliminates the simplest cause.
5.Unplug the "B" connector and inspect it against the "A" connector side by side. Comparing the two makes corrosion, terminal spread, and seal damage obvious in a way examining one alone does not.
6.Check terminal tension against a matching pin rather than by eye, since a terminal that has lost grip still looks normal in the housing.
7.Measure the "B" actuator's coil resistance and compare it against the healthy "A" actuator on the same engine, provided both positions take the same part. A same-engine reference is more reliable than a generic chart value.
8.With the actuator unplugged and the circuit not commanded, check the control wire for an unintended path to ground.
9.Check end-to-end continuity of the control wire between the module connector and the "B" connector to find an open.
10.Test the "B" channel ground for low resistance under a small load rather than trusting a continuity beep.
11.Follow the "B" harness along its full route looking for shiny flattened chafe points and stiff dark brittle heat-damaged sections, paying attention to where it passes near exhaust components.
12.Wiggle-test the harness and connector at operating temperature while watching live data.
13.Do not swap the "A" and "B" actuators to see whether the fault follows unless you have confirmed the part numbers match, since a mismatched part creates a second fault on top of the first.
14.Check manufacturer service bulletins for known harness and connector issues on your engine.
15.Suspect the module driver only after the fuse, connector, coil, control wire, and ground have all been verified good.

Repair cost

$90 – $1,600

Like the "A" circuit-low code, this one resolves cheaply more often than the family average because electrical faults on this circuit are usually connectors. A connector or terminal repair typically lands at $130-$450, and cleaning and re-terminating a corroded connector is a common outcome. Diagnosis runs $150-$300. A fuse or relay replacement is $20-$120. Tracing and repairing a short to ground or an open generally runs $250-$800 on the "B" harness — more than the "A" equivalent because the route is usually longer and less accessible, and heat-damaged sections near the exhaust need replacing rather than splicing. A "B" metering actuator is $90-$450 in parts with 1-4 hours of labor, or roughly $250-$1,100 installed, and considerably more on engines where the second pump must be disturbed to reach it. The upper end reflects harness replacement where the affected section is not separately serviceable.

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DIY vs shop

This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.