P0273 — Cylinder 5 Injector Circuit Low #
The code description may vary depending on the manufacturer.
- “Cylinder 5 Injector Circuit Low” (General, Ford, GM, Chrysler)
- “Injector 5 Control Circuit Low Voltage” (Toyota, Honda)
- “Cyl 5 Inj Low Input” (Nissan)
- “F5 Injector Circuit Signal Low” (BMW, Mercedes-Benz)
Summary of the P0273 Code #
P0273 is a diagnostic trouble code (DTC) indicating that the engine control module (ECM) has detected a low voltage condition in the electrical circuit controlling injector number 5. This code is tied to the OBD-II (On-Board Diagnostics, Second Generation) system, which is standard across most vehicles built after 1996. Fuel injectors are electro-mechanical devices responsible for delivering precise amounts of fuel into the engine’s combustion chamber. When the circuit for cylinder 5’s injector is reading lower than expected voltage, it usually means the injector isn’t functioning properly, potentially leading to poor engine performance or drivability issues. The cause can range from a simple wiring problem to a failed injector or ECM fault.
Common Symptoms for P0273 #
When the P0273 code is present, drivers and technicians may notice a range of symptoms, often linked to rough engine operation. Since injector number 5 may not be supplying proper fuel, the engine can misfire or run unevenly. The Check Engine Light (CEL) will almost always be illuminated, but additional behaviors may also signal this fault.
- Illuminated Check Engine Light
- Rough idle, especially when cold
- Poor acceleration or hesitation
- Noticeable engine misfire
- Reduced fuel economy
- Possible loss of power under load
- Occasional engine stalling
Probable Causes for P0273 #
The most common reasons for the P0273 code relate to either electrical faults or mechanical failure of the injector itself. These causes are listed in order of frequency based on field experience and OEM documentation.
- Faulty or failing fuel injector (cylinder 5)
- Damaged or corroded injector wiring/connectors
- Open or short circuit in injector harness
- ECM/PCM (Engine/Powertrain Control Module) failure
- Poor electrical ground near injector 5
- Fuse or relay issue related to injector power supply
Step-by-Step Diagnostic for P0273 #
Diagnosing P0273 involves a systematic approach to rule out common issues and confirm the root cause. Always start with the basics and move toward more complex checks, using a digital multimeter and scan tool when necessary.
- Verify the P0273 code and look for related injector or misfire codes using a scan tool.
- Visually inspect the injector 5 wiring harness and connector for damage, corrosion, or loose pins.
- With the ignition off, disconnect the injector 5 connector and check for bent terminals or moisture ingress.
- Using a multimeter, measure resistance across injector 5; compare it to other injectors—significant deviation indicates a faulty injector.
- Check for continuity between the ECM connector pin (for injector 5) and the injector plug; a break or high resistance points to wiring issues.
- Inspect for proper voltage at the injector connector with the ignition on; a missing or low reading may suggest a power or ground issue.
- If all wiring and injector checks are normal, consider ECM/PCM testing or replacement as a last resort.
Possible Repairs for P0273 #
Once the source of the P0273 code is identified, repairs can be targeted and efficient. Addressing the exact fault will restore injector function and overall engine performance.
- Replace cylinder 5 fuel injector if resistance or spray test confirms failure.
- Repair or replace damaged wiring or connectors in the injector 5 circuit.
- Clean corroded terminals and apply dielectric grease to protect against moisture.
- Restore or reattach poor ground connections linked to injector circuit.
- Replace blown fuses or faulty relays supplying power to the injector bank.
- Replace or reprogram ECM/PCM only if all other diagnostics are exhausted and confirmed.
Is It Safe to Drive with Code P0273? #
Limited: It is generally not recommended to drive extensively with a P0273 code active. While the vehicle may still run, performance will be degraded, and continued operation can lead to further engine damage, such as fouled spark plugs or catalytic converter overload from unburned fuel. Short, slow drives to a service facility are usually acceptable, but the issue should be addressed promptly to avoid escalation.
Vehicles Most Commonly Affected by P0273 #
While P0273 can appear on any OBD-II equipped vehicle, certain makes and models are reported more frequently in technical forums and OEM bulletins. This often correlates to engine layout or common injector harness routing.
- Ford F-Series (V8 engines, various years)
- Chevrolet Silverado and GMC Sierra (V8 engines)
- Dodge Ram 1500/2500 (Hemi engines)
- BMW 3 Series and 5 Series (inline-6 and V8)
- Toyota Tundra and Sequoia (V8)
- Honda Odyssey (V6)
- Mercedes-Benz E-Class (V6/V8)
Common Mistakes & Best Practices for P0273 #
Misdiagnosis or skipping steps can lead to unnecessary parts replacement and frustration. Always start with the basics and use OEM wiring diagrams whenever possible.
- Replacing the fuel injector without first testing the wiring harness and ECM outputs.
- Overlooking corroded or loose ground connections, which can cause intermittent faults.
- Neglecting to clear the code and perform a test drive after repairs to confirm success.
- Assuming all injectors fail the same way; always compare cylinder 5 to others for context.
- Not checking for related DTCs that could point to a larger harness or power distribution issue.
Quick FAQ for P0273 #
Here are fast answers to common questions about this code.
- Q: Will a fuel injector cleaner fix P0273?
A: No. P0273 is an electrical circuit fault, not a clog or deposit issue. Injector cleaner will not resolve wiring or ECM problems. - Q: Can I swap injectors to test for P0273?
A: Sometimes. If the code moves to another cylinder after swapping injectors, the injector is faulty. If it stays on cylinder 5, the problem is likely in the wiring or ECM.
