OBD-II trouble code
P2152: Fuel Injector Group "C" Supply Voltage Circuit/Open
A third branch changes the maths. With groups A and B both alive, you no longer have one reference to measure against — you have two that agree with each other, and a suspect that disagrees with both. That majority vote is not available on a two-branch engine, and it is the reason this code is usually faster to pin down than its A and B counterparts.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $20 – $850
- DIY difficulty
- Intermediate DIY
Browse every code in P2100–P2199, or start from the full code library.
What does P2152 mean?
P2152 says the positive feed to the third injector supply branch — the one this manufacturer indexes as group C — has gone open or lost continuity. The letter itself is only a label. What matters is the arithmetic implied by there being a third one at all.
Two-branch designs are ordinary. Three is a deliberate choice, and engines that make it fall into a few recognisable camps: high cylinder counts where four injectors per branch would push a relay contact past its rating, engines with a staged or sequential strategy that groups injectors by firing order rather than by bank, and installations where an extra set of injectors exists for a second fuel or for extra fuelling under boost. In every one of those cases the designer split the load because a single branch could not carry it comfortably, which is worth remembering when you start measuring: these branches are running closer to their limits than a two-branch layout would.
The practical consequence for the driver is that losing one of three branches is a smaller loss than losing one of two. More of the engine keeps working, the shake is milder, and the power loss is real but not alarming. That sounds like good news and is actually the trap — a car that merely feels flat and slightly rough gets driven for weeks, while the same fault on a two-branch engine would have been on a flatbed the same afternoon. Expect these to arrive late, with fouled plugs and a soaked catalytic converter already part of the bill.
The diagnostic advantage is the part worth planning around. On a two-branch engine the healthy branch is your reference, and that works right up until the healthy branch is also degraded — in which case the comparison quietly misleads you, and nothing in the measurement tells you so. With three branches, you take the same reading at all three points. Two of them agreeing, with the third adrift, is a clean verdict on the third. All three agreeing means the fault is upstream of where they divide, not on any branch. And the case that a two-branch engine simply cannot detect — two readings adrift together, one normal — tells you the supply feeding the pair is the problem, or that your assumed-good reference never was good. That is a majority vote rather than a comparison, and it is strictly more information for the same effort.
One caution before you start unwrapping loom. Group C is not automatically a set of cylinders. On engines with a second injector rail — port-plus-direct petrol, or a gaseous-fuel conversion — a group can be an entire fuel system rather than a subset of the cylinders, in which case the misfire pattern that identifies A and B branches so neatly will not appear at all. Confirm from the wiring diagram for this exact engine what group C actually feeds before deciding what to test.
Where the open lives is the usual list — fuse, relay, the distribution point where the branches separate, then the branch run and its connectors. What changes on a three-branch engine is that the distribution point is carrying more parallel load in a smaller space, so the stud, splice pack or bus bar where all three take their supply is a higher-probability failure point than it would be on a simpler layout, and it is worth checking early rather than last.
Common causes
- Open or failed splice at the distribution point where the supply divides into three branches
- Blown fuse dedicated to the third injector branch
- Relay or relay socket serving group C with a burnt, spread or backed-out terminal
- Loose or corroded supply stud where multiple branches land on one post
- Broken conductor in the group C branch run, often at a flex point behind the engine
- Corroded supply terminal at one of the group C injector connectors
- Chafed or melted branch wiring where it passes close to exhaust or turbocharger heat
- Damaged wiring on a secondary injector rail on port-plus-direct or dual-fuel engines
- Connector left unmated after injector, manifold or rail work
- Failed injector driver supply stage inside the engine control module
Symptoms
- Noticeable but not dramatic loss of power, often described as the car feeling flat
- Rough running that is milder than a total branch failure because more cylinders keep working
- Misfire codes on a consistent group of cylinders, or on no cylinders at all if the branch feeds a second fuel rail
- Check engine light on, sometimes for weeks before the car is brought in
- Poor cold start or hesitation at low load on engines where the branch feeds port injectors
- Fuel smell or fouled spark plugs from prolonged driving with the fault present
- Fuel trims skewed on one bank while the other reads normally
- Failed emissions test with no obvious driveability complaint
- Fault that appeared immediately after work near the injector rail or distribution point
- Reduced power or limp mode on engines that detect the branch loss directly
Diagnostic steps
- 1.Establish from the wiring diagram for this specific engine what group C feeds — a set of cylinders, or an entire secondary injector rail. The two lead to completely different tests.
- 2.Take the same key-on supply measurement at all three branches rather than at two. Two matching values with one adrift is a verdict; three matching values sends you upstream of the split.
- 3.Treat a result where two branches read low together as information, not noise. That pattern points at the shared feed or distribution point and is invisible on a two-branch engine.
- 4.Inspect the distribution stud, splice pack or bus bar where the branches separate. On a three-branch layout it carries the most parallel current in the smallest space and is a high-probability failure point.
- 5.Check the fuse and relay for the affected branch, swapping them with an identical branch's components if the design uses separate ones, so the fault can be made to follow the part.
- 6.Back-probe the supply pin at a group C injector connector and compare directly against the equivalent pin on both healthy branches at the same moment.
- 7.Work outward from the split point rather than inward from the injectors, so the open is bracketed between a confirmed-good and a confirmed-bad measurement.
- 8.Follow the branch along its physical route with particular attention to heat exposure, since three-branch engines are usually larger and route wiring further around the block.
- 9.Drag-test each supply terminal in the group C connectors rather than judging contact by eye, and look for pushed-out or heat-discoloured pins.
- 10.After repair, confirm all three branches now read within a few tenths of a volt of each other under load, and clear the misfire history before road testing.
Repair cost
$20 – $850
A fuse is a few dollars and a relay $15 to $60 fitted. Diagnosis runs $110 to $250, and a three-branch engine tends to land at the lower end because the two healthy branches settle questions a single reference cannot. Repairing the distribution splice or supply stud where the branches divide is $130 to $400. A branch wiring repair is $150 to $500 and rises where the run is long and buried, which it usually is on the larger engines that use three branches. Connector and terminal repair is $90 to $220. If the supply stage inside the control module has failed, replacement and programming is $600 to $1,500. Replacing injectors, at $400 to $1,200, addresses nothing here.
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DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.