OBD-II trouble code
P0273: Cylinder 5 Injector Circuit Low
The cylinder 5 injector control circuit read low — usually a wire shorted to ground or a shorted injector coil. Cylinder 5 only exists on six-, eight- and twelve-cylinder engines, so confirm which bank it is on before testing.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Medium severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $50 – $1,500
- DIY difficulty
- Intermediate DIY
What does P0273 mean?
The engine control module (ECM) switches fuel injectors on the ground side. Switched battery voltage sits on one injector terminal, and the ECM fires the injector by pulling the other terminal to ground for a precisely metered pulse width. Between pulses that control wire should sit near battery voltage, because nothing should be tying it to ground.
P0273 sets when the ECM sees the cylinder 5 control circuit reading low while it expects high — the circuit is grounded when it should be floating. In practice that means a control wire that has chafed through and touched the block, the head, or a bracket, an injector with a shorted coil winding, or corrosion and moisture bridging pins inside the connector. On some platforms the code also sets when measured current through the circuit falls below the expected range.
P0273 is the first code in the per-cylinder injector block where the cylinder itself is not universal. Four-cylinder engines have no cylinder 5, so this code only appears on inline sixes, V6s, V8s, inline fives, V10s and V12s — and on those engines cylinder 5 is almost never where an untrained guess would place it. On most General Motors V8s, cylinder 5 is the second cylinder back on the driver's-side bank (1-3-5-7). On most Ford modular V8s, the driver's side is 5-6-7-8, so cylinder 5 is the frontmost cylinder on that bank. On a transverse V6 the numbering may run front bank first or rear bank first depending on the manufacturer. Getting this wrong means testing a perfectly good injector, so look up the numbering diagram for your specific engine before a single connector comes apart.
Electrically the consequence is the same as on any cylinder: cylinder 5 is not being fueled the way the ECM intends, so a misfire is likely and P0305 often appears alongside. That misfire is why the code deserves prompt attention. Raw air and unburned fuel entering the exhaust can superheat the catalytic converter, and a converter costs far more than repairing a wire or replacing one injector.
Common causes
- Cylinder 5 injector control wire chafed through and shorted to ground
- Shorted coil winding inside the cylinder 5 injector
- Corrosion or water intrusion bridging terminals in the injector connector
- Harness insulation heat-damaged where it crosses the exhaust manifold or turbocharger on that bank
- Wire pinched during a prior intake manifold, valve cover, or head gasket repair
- Damaged, spread, or backed-out terminal in the injector connector
- Rodent or abrasion damage to the injector harness along the rear or inner side of the bank
- Rarely, a failed cylinder 5 injector driver circuit inside the ECM/PCM
Symptoms
- Check engine light on, sometimes flashing under load
- Rough idle with a noticeable engine shake
- Misfire on cylinder 5, commonly with a companion P0305
- Loss of power and hesitation under acceleration
- Raw fuel smell from the exhaust
- Increased fuel consumption
- Hard starting or extended cranking in some cases
Diagnostic steps
- 1.Confirm P0273 and record all companion codes. A cylinder 5 misfire (P0305), the paired high code P0274, or a balance fault (P0275) each shift the diagnostic emphasis.
- 2.Look up the cylinder numbering diagram for your exact engine and physically identify cylinder 5 before touching anything. GM V8s put 5 on the driver's bank as the second cylinder back; Ford modular V8s put 5 at the front of the driver's bank; V6 banks vary by manufacturer.
- 3.Inspect the cylinder 5 injector connector and pigtail for corrosion, melted or hardened insulation, and backed-out terminals. Follow the harness where it passes near exhaust heat on that bank.
- 4.With the key off, unplug the injector and measure its coil resistance. Compare it to specification and to the other injectors — a reading well below spec confirms a shorted coil.
- 5.Disconnect both the injector and the ECM connector, then check the control wire for continuity to ground. Any continuity confirms a short in the harness rather than a bad injector.
- 6.Wiggle-test the harness along the whole bank, focusing on chafe points at manifold studs, hard bracket edges, and anywhere the loom has worn thin.
- 7.With the wiring and injector verified good, use a noid light or the scan tool's injector test to confirm the ECM is pulsing the circuit normally.
- 8.If everything external tests correct and the drive signal is still wrong, suspect the ECM injector driver — verify with the manufacturer's pinout test before condemning the module.
Repair cost
$50 – $1,500
Repairing a chafed wire or a corroded connector is often $75-$250. A single fuel injector is $60-$400 in parts plus 0.5-3 hours of labor — an accessible port injector is quick, but a cylinder 5 injector buried under an intake manifold on a V6 or V8 takes considerably longer, and a diesel injector on an inline six commonly lands at $400-$900 installed. A failed ECM injector driver is uncommon and runs $500-$1,500 including programming. Diagnosis alone is typically $75-$150.
Estimate your repair
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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.