OBD-II trouble code
P2291: Injector Control Pressure Too Low - Engine Cranking
Pressure failed to come up during the crank. Cranking is the hardest test this system ever faces, because the pump is turning at a tenth of its normal speed while its leakage barely slows down at all.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $90 – $3,200
- DIY difficulty
- Advanced DIY
Browse every code in P2200–P229F, or start from the full code library.
What does P2291 mean?
The qualifier on the end of this title is not decoration, and it is the reason a separate address exists at all. Cranking asks the high-pressure oil circuit to do something it never has to do again during the drive: build from nothing, quickly, while being turned at starter speed.
The arithmetic behind that is worth spelling out, because it explains almost every odd thing about this code. A positive-displacement pump moves a volume per revolution, so its delivery is proportional to how fast it is being turned. Leakage past a clearance, by contrast, is driven mainly by the pressure across it and hardly cares about engine speed at all. Turn the engine at 200 rpm on the starter instead of 2,000 rpm running, and delivery drops by a factor of ten while the losses stay roughly where they were. A leak that consumes a twentieth of the pump's output at idle can be consuming half of it during the crank. This is precisely why a vehicle can set P2291 on its own, with no running pressure complaint whatsoever: the same defect that dominates at starter speed is comfortably outrun the moment the engine fires and spins the pump properly.
That reframing matters because it points diagnosis somewhere unexpected. If cranking speed is the variable that decides whether this system makes pressure, then anything that slows the crank is a legitimate cause of a fuel code. A tired battery, corroded cables, a poor engine-to-body ground or a starter drawing more current than it should will all knock a further slice off pump speed, and on a system with no margin left that slice is the difference between starting and not. Measuring cranking rpm and battery voltage under load is the correct first move here, and it is skipped constantly because the code has the word injector in it.
The complaint pattern usually confirms the mechanism before any tool comes out. The engine that starts fine when warm and refuses after sitting overnight is describing drain-down: the high side has emptied back to the sump through a seal or a joint that holds well enough under running conditions, so the crank has to refill the gallery before it can pressurise it. The one that fails the first attempt and fires on the second is telling you the same thing more precisely, because that first crank did the filling and the second only had to do the pressurising. An engine that cranks endlessly no matter how many attempts you make is saying something different and worse, which is that delivery is not happening at all.
One practical warning belongs on every diagnosis of this code. Long cranking is itself destructive to the parts you are trying to evaluate. Extended starter operation heats the starter and flattens the battery, which lowers cranking speed further and makes the next attempt worse than the last, so a hard-start complaint tends to deteriorate on its own while you are testing it. Work in short attempts with recovery time between them, and put a charger on the battery before you draw conclusions from anything.
Common causes
- High-pressure oil draining back overnight through an injector seal, standpipe or gallery joint
- Slow cranking from a weak battery, corroded cables or poor grounds, reducing pump speed
- Worn high-pressure oil pump unable to deliver enough volume at starter speed
- Engine oil too heavy for the ambient temperature, slowing the fill during the crank
- Low engine oil level leaving the pump inlet uncovered on the first revolutions
- Injector pressure regulator valve resting open and preventing the gallery from charging
- Starter motor drawing excess current and dragging cranking speed down
- Injector control pressure sensor reading low and masking a pressure that is actually present
Symptoms
- Long crank before the engine catches, or a complete no-start
- Starts normally when warm but refuses after sitting overnight
- Fails the first start attempt and fires on the second or third
- Cranking sounds slower or more laboured than it used to
- Puff of smoke on the eventual start followed by normal running
- Engine runs acceptably once started, with no power complaint
- Problem clusters in cold weather and eases as the season warms
Diagnostic steps
- 1.Measure cranking speed and battery voltage under load before touching the hydraulic side. If the engine is turning slowly, the pump is being denied the one thing it needs and no hydraulic test result will mean anything.
- 2.Check oil level, grade and condition. A cold-morning no-start on oil far heavier than specified is a routine finding and costs nothing to rule out.
- 3.Watch the pressure reading rise in real time during a crank rather than reading a single value. The shape of the climb separates a system that fills slowly from one that never climbs at all.
- 4.Note whether a second consecutive crank behaves better than the first. Improvement points at drain-down and refill; no improvement points at delivery.
- 5.Leave the vehicle to sit for several hours and watch the first crank of the day, because a monitor that only runs during cranking cannot be reproduced any other way.
- 6.Inspect the injector bodies, standpipes and gallery joints for oil migration, which is where a system that empties overnight is usually losing it.
- 7.Verify starter current draw if cranking speed is marginal. A starter that is dragging is a fuel-system cause on this engine even though it has nothing to do with fuel.
- 8.Assess pump delivery only after cranking speed, oil supply and drain-down have all been excluded.
Repair cost
$90 – $3,200
A battery, cable or ground repair that restores cranking speed is the cheap end at $90 to $450 and is a more common fix than the code's wording suggests. An oil service with the correct grade is $90 to $200. Injector seal or standpipe work to stop overnight drain-down runs $400 to $1,400 depending on access. A control pressure sensor is $150 to $400 fitted. A high-pressure oil pump sits at the top at $1,400 to $3,200 fitted. Expect $150 to $300 of diagnostic time, partly because reproducing a cranking-only fault often means the vehicle has to be left overnight.
Estimate your repair
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Open the Repair Cost Estimator with high-pressure oil pump replacement preselected. Adjust labor rate and vehicle category to fit your situation.
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.