OBD-II trouble code
P0280: Cylinder 7 Injector Circuit High
The cylinder 7 injector control circuit read higher than expected — an open circuit or a short to battery voltage. Check the injectors' shared power feed before condemning the injector, especially if other cylinders set codes too.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Medium severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $30 – $1,500
- DIY difficulty
- Intermediate DIY
What does P0280 mean?
P0280 is the opposite condition from P0279 on the same circuit. The engine control module (ECM) fires the cylinder 7 injector by pulling its control wire to ground, and it monitors that wire to confirm the voltage actually drops when it commands a pulse. P0280 sets when the voltage stays high — the ECM tried to pull the circuit down and the circuit did not follow.
Only two conditions produce that result. The first is an open circuit: a broken conductor, a disconnected or corroded connector, or an injector with a broken coil winding leaves the ECM's ground path connected to nothing, so the voltage never drops. The second is a short to battery voltage, where another power source is feeding the control wire and holding it up against the module. Both look identical from inside the ECM, and separating them with two measurements is the whole diagnosis.
On an eight-cylinder engine there is one check worth doing before anything else, because it can explain several codes at once. Injectors are not fed power individually — they are grouped, very often one group per bank, through a common fuse and relay or a single feed wire that splices out to each injector on that side. If the feed to cylinder 7's group is lost, the ECM's control-side measurement goes abnormal on every injector in the group, and no amount of injector replacement will fix any of them. So if P0280 arrived together with high codes on other cylinders that share its bank, the shared feed is the prime suspect. Put the key on, back-probe two or three injector connectors on that bank, and look for battery voltage. If it is absent at all of them, one repair — a fuse, a relay, or a feed wire — clears every code.
If the feed is present and only cylinder 7 is affected, the fault is local: an open in that one control wire, an open injector winding, or that wire shorted to power. On a V8, cylinder 7 is a rearward cylinder on one bank, where the harness runs past exhaust heat and collects moisture from the cowl — conditions that crack insulation and corrode terminals. Confirm which physical cylinder your manufacturer calls number 7 before testing; GM and Ford V8s number their banks differently and testing the wrong cylinder wastes the entire diagnosis.
With the circuit stuck high, cylinder 7 receives little or no fuel, so a misfire is essentially certain and P0307 commonly appears with it. Unburned fuel and air entering the exhaust can overheat and ruin the catalytic converter on that bank.
Common causes
- Loss of the switched power feed shared by that bank's injectors — a blown fuse or a failed relay
- Open circuit in the cylinder 7 injector control wire (broken conductor or corroded splice)
- Open coil winding inside the cylinder 7 injector
- Injector connector unplugged, unlatched, or with a spread or corroded terminal
- Control wire shorted to battery voltage or to another powered circuit
- Cracked, heat-hardened insulation letting the control wire contact a powered stud or terminal
- Connector left unseated after intake manifold, valve cover, or exhaust work
- Rarely, a failed cylinder 7 injector driver inside the ECM/PCM
Symptoms
- Check engine light on, sometimes flashing under load
- Dead or very weak cylinder 7 with a rough, shaking idle
- Misfire codes such as P0307 or P0300 stored alongside
- Marked loss of power and hesitation
- Raw fuel odor from the exhaust
- Poor fuel economy
- Hard starting or extended cranking
- Multiple injector high codes on the same bank when a shared feed has failed
Diagnostic steps
- 1.Confirm P0280 and record every companion code. High codes on multiple cylinders of the same bank point at a shared power feed rather than at the injectors.
- 2.With the key on, back-probe two or three injector connectors on the affected bank and confirm battery voltage on the feed side. Missing voltage at all of them means the fault is a fuse, a relay, or the feed wire — one repair clears every code.
- 3.Identify cylinder 7 for your specific engine in the service information. GM V8s number the driver's bank 1-3-5-7; Ford modular V8s number it 5-6-7-8.
- 4.Inspect and fully reseat the cylinder 7 injector connector. A connector left unlatched after prior service or a backed-out pin is a common and free fix.
- 5.Unplug the injector with the key off and measure its coil resistance. An infinite or very high reading confirms an open winding and condemns the injector.
- 6.Disconnect both the injector and the ECM connector and check the control wire end to end for continuity. No continuity confirms an open in the harness.
- 7.With the ECM connector still disconnected, check the control wire for unexpected voltage. Voltage present there means the wire is shorted to a power source that must be located and repaired.
- 8.Once the wiring and injector both test correct, use a noid light or a scan tool injector test to verify the ECM is actually pulsing the circuit before considering the module.
Repair cost
$30 – $1,500
A blown fuse or failed injector relay is often under $100, and an unlatched connector costs nothing but time — worth checking first because these are the cheapest possible outcomes. Repairing a broken or shorted wire is typically $75-$250. A single fuel injector is $60-$400 in parts plus 0.5-3 hours of labor, with rear-of-bank access on a V8 pushing toward the upper end. Diesel V8 injectors commonly run $400-$900 each installed. A failed ECM injector driver is uncommon and runs $500-$1,500 including programming. Diagnosis alone is typically $75-$150.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with fuel injector replacement preselected. Adjust labor rate and vehicle category to fit your situation.
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.