OBD-II trouble code
P0283: Cylinder 8 Injector Circuit High
The engine computer saw higher-than-expected voltage on the cylinder 8 injector control wire, meaning the circuit is open or shorted to power. If several injector high codes set at once, check the shared power feed before you buy a single injector.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Medium severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $20 – $1,500
- DIY difficulty
- Intermediate DIY
What does P0283 mean?
The engine control module (ECM) fires each injector by supplying battery voltage to one side and pulling the other side to ground for a measured number of milliseconds. When the ECM commands the ground and the control line stays high instead of dropping, the current it expected never flowed. P0283 is that observation, isolated to the cylinder 8 injector circuit.
Only two conditions produce it. The circuit is open — a broken wire, a disconnected or backed-out connector pin, or an injector coil that has burned open internally. Or the control wire is shorted to a source of voltage that overwhelms the ECM's attempt to pull it low. That is a genuinely useful narrowing. A circuit LOW code has three plausible causes that all look alike on a scan tool; a circuit HIGH code has two, and two measurements cover the entire space. Check the injector's coil resistance, then check the control wire for continuity to the ECM. Whichever one fails is your answer.
Before any of that, though, there is one check worth doing first because it can explain the whole thing for the price of a fuse. On V8 and larger engines, injectors are almost never fed individually. They are supplied in groups — very often one group per bank — through a common fuse, relay, or splice. If that shared feed opens, every injector downstream of it loses power at once, and the ECM reports a circuit high code for each of them. If you are looking at P0283 alongside other cylinders' high codes, and especially if the affected cylinders all sit on one bank, do not start replacing injectors. Back-probe two or three connectors on that bank for battery voltage with the key on. No voltage means one upstream repair clears every code, and every injector in the group is fine.
Cylinder 8 is the rearmost cylinder on a bank on essentially every V8, which makes it the hardest injector to reach and the one most exposed to heat cycling and cowl water. It is also the code where the manufacturer numbering convention bites hardest: GM V8s number the passenger bank 2-4-6-8 and Ford modular V8s number the driver's bank 5-6-7-8, so the two conventions place cylinder 8 on opposite sides of the engine. Confirm your numbering before you disassemble anything.
An open injector circuit means cylinder 8 gets no fuel at all. The engine runs on seven cylinders, and the unburned oxygen and fuel passing into the exhaust will cook the catalytic converter on that bank. Treat this as a repair-now code rather than a monitor-for-a-while one.
Common causes
- Open circuit in the cylinder 8 injector control or power wiring
- Blown injector fuse or a failed relay feeding the bank's injector group
- Corroded, spread, or backed-out terminal in the cylinder 8 injector connector
- Injector connector not fully seated after intake manifold or valve cover work
- Open coil winding inside the cylinder 8 injector
- Control wire shorted to battery voltage where the harness has chafed against a bracket or the exhaust
- Corroded splice or connector in the shared injector power feed at the rear of the engine
- Failed cylinder 8 injector driver inside the ECM/PCM (rare — verify everything else first)
Symptoms
- Check engine light on, frequently flashing because cylinder 8 is dead
- Rough idle with a strong shake
- Clear power loss, hesitation, and a rough-running engine
- Companion cylinder 8 misfire code (P0308), often with P0300
- Hard starting or extended cranking
- Poor fuel economy
- Multiple injector circuit high codes at once if a shared feed has failed
Diagnostic steps
- 1.Read all stored codes first. If more than one injector circuit high code is present, map the affected cylinders to banks — a whole-bank pattern points at the shared power feed, not at the injectors.
- 2.Back-probe the cylinder 8 injector connector for battery voltage on the feed side with the key on. No voltage means the fault is upstream, and one repair to the fuse, relay, or splice clears every related code.
- 3.Check the injector fuse and relay for the bank before doing anything else. This is the cheapest possible outcome and takes minutes.
- 4.Confirm which physical cylinder your engine calls number 8 — GM V8s place it at the rear of the passenger bank, Ford modular V8s at the rear of the driver's bank.
- 5.With the key off, measure the cylinder 8 injector's coil resistance and compare against specification and the other injectors. An infinite or very high reading confirms an open winding.
- 6.Check continuity on the control wire from the injector connector back to the ECM pin. An open confirms a broken wire; near-battery voltage present with the key on and the connector unplugged suggests a short to power.
- 7.Inspect the connector for spread female terminals, corrosion, and full seating. A terminal that has lost its grip reads as an open circuit intermittently and returns after any repair that does not address it.
- 8.Wiggle-test the harness and connector with the engine running while watching live data, to catch an intermittent open.
- 9.Only after the fuse, feed, wiring, and injector all check out should you suspect the ECM injector driver, since replacement requires programming.
Repair cost
$20 – $1,500
A blown injector fuse can be a few dollars, and that outcome is more common on this code than most people expect. A wiring or connector repair is usually $50-$250. A single fuel injector runs $60-$400 in parts plus 0.5-3 hours of labor, with cylinder 8 near the top of the labor range on virtually every V8 because it is the rearmost injector and often sits under the upper intake plenum, which adds gaskets. Direct-injection units cost more. A failed ECM injector driver is rare and runs $500-$1,500 with programming. Diagnosis alone is typically $100-$180.
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.