Diagnostic trouble code P1243 is a manufacturer-specific powertrain fault code. Because it is manufacturer-specific, its exact definition depends entirely on the vehicle make, model, and application.
Exact vehicle application must be verified before diagnosis. The code identifies a detected condition in a specific subsystem, but further testing is required to identify the root cause.
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Key Takeaways
- P1243 is a manufacturer-specific code, meaning its definition varies significantly between automakers like Ford, Volkswagen, General Motors, and Nissan.
- On Ford applications, it typically indicates a second fuel pump fault or a secondary fuel pump circuit ground fault.
- On Volkswagen and Audi applications, it points to a cylinder 7 fuel injector open circuit.
- On certain GM and Vauxhall applications, it indicates a turbocharger bypass or surge valve solenoid circuit fault.
P1243 Code Description and Implications
Because P1243 is manufacturer-specific, there is no single universal definition. This fault code identifies a detected condition, but the exact monitored system depends on the vehicle make and model.
Some Ford and Lincoln applications: P1243 indicates a “Second Fuel Pump Faulty or Ground Fault,” meaning the powertrain control module detects an electrical issue in the secondary fuel pump circuit.
Certain Volkswagen and Audi applications: P1243 indicates a “Cylinder 7 Injector Circuit Open Circuit,” pointing to an electrical open in the fuel injector control circuit for cylinder 7.
Some GM, Vauxhall, and Opel applications: P1243 indicates a “Turbocharger Surge Valve Solenoid Control” or bypass valve circuit fault, meaning the module detects an open or short in the turbo bypass solenoid circuit.
Certain Nissan and Infiniti applications: P1243 indicates a “Supercharger Bypass Valve Circuit Malfunction,” pointing to an electrical fault in the supercharger bypass valve control circuit.
Common Causes of the P1243 Code
The underlying cause depends entirely on the verified factory definition for the specific vehicle application.
For Ford applications, possible causes include a failing secondary fuel pump, damaged wiring in the fuel pump circuit, poor electrical connections, or a failing fuel pump control module.
For VW and Audi applications, causes may involve a failing cylinder 7 fuel injector, damaged injector wiring, or poor connector contacts at the injector harness.
For GM and Vauxhall applications, causes can include a failing turbocharger bypass valve solenoid, damaged vacuum or electrical lines, or poor solenoid grounds.
Symptoms Associated With P1243
Symptoms vary depending on the underlying system fault and the vehicle manufacturer.
On Ford applications with a secondary fuel pump fault, symptoms can include poor engine performance, stalling under load, and decreased fuel economy.
On VW and Audi applications with an injector circuit fault, symptoms often include severe engine misfires, rough idling, loss of power, and an illuminated Check Engine Light.
On GM and Vauxhall applications with a turbo bypass valve fault, symptoms may include reduced boost pressure, poor acceleration, and a flashing or solid Check Engine Light.
Diagnosing the P1243 Trouble Code
Diagnosis must begin by confirming the exact factory definition for the specific make, model, and year.
For Ford applications, technicians inspect the secondary fuel pump wiring for opens or shorts, test the pump operation, and verify the fuel pump control module signals.
For VW and Audi applications, technicians test the cylinder 7 injector circuit resistance, inspect the injector wiring for opens, and verify the control module driver signals.
For GM and Vauxhall applications, technicians test the turbo bypass solenoid operation, inspect the solenoid wiring, and verify vacuum supply to the bypass valve.
Repairing the P1243 Issue
Repairs must follow confirmed diagnosis based on the specific vehicle application.
If a secondary fuel pump circuit fault is confirmed on a Ford application, the damaged wiring must be repaired or the secondary fuel pump assembly replaced.
If a cylinder 7 injector open circuit is confirmed on a VW or Audi application, the failing fuel injector or damaged wiring must be replaced.
If a turbo bypass valve circuit fault is confirmed on a GM or Vauxhall application, the failing solenoid or damaged wiring must be replaced.
Cost Considerations for P1243 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Replacing a turbo bypass solenoid or repairing damaged wiring may require minimal labor depending on accessibility.
Conversely, replacing an in-tank secondary fuel pump or accessing a buried fuel injector requires significant labor, as it often involves dropping the fuel tank or removing the intake manifold.
Prevention Strategies for Future Occurrences
Some electrical and mechanical failures cannot be reliably prevented.
Inspecting exposed engine bay and undercarriage wiring harnesses for chafing, heat damage, or moisture intrusion can help prevent intermittent circuit faults in solenoid and pump systems.
Keeping electrical connectors clean and ensuring connector seals remain intact may reduce corrosion that leads to open circuit failures.
Troubleshooting Tips and Best Practices
Never assume P1243 is a universal fuel pump or injector code. Always verify the exact definition for the specific vehicle before purchasing parts.
Do not ignore related codes. A fuel pump fault may appear alongside other fuel pressure codes, while an injector fault may appear alongside multiple cylinder misfire codes.
Check for technical service bulletins applicable to your exact vehicle application, as manufacturers frequently release updated wiring harnesses or revised solenoid components for recurring faults.
More OBD-II Codes
| P1225 | P1244 | P1240 | P0171 |
| P1224 | P1245 | P1237 | P0174 |
| P1223 | P1250 | P1234 | P0300 |
| P1222 | P1251 | P1231 | P0420 |
| P1221 | P1252 | P0172 | P0430 |
| P1220 | P1253 | P0173 | P0135 |
Frequently Asked Questions
Is P1243 a generic or manufacturer-specific code?
No. P1243 is a manufacturer-specific code. Its exact definition varies significantly between automakers, so the factory service information for the specific vehicle must be consulted.
Can I drive my car with a P1243 code?
It depends on the application. If P1243 indicates a severe misfire from an injector fault or a turbo bypass fault, continuing to drive may cause catalyst damage or severe power loss.
Will disconnecting the battery clear the P1243 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying electrical or mechanical fault. The code will return once the monitor runs again.
Can a bad fuel pump relay cause a P1243 code?
On applications monitoring the secondary fuel pump circuit, a failing relay or poor relay connection can interrupt power to the pump, causing the control module to detect a circuit fault.
Does P1243 always mean the fuel pump or injector is bad?
No. While a failing component is a cause on specific applications, the code can also indicate damaged wiring, a short to ground, an open circuit, or a poor electrical connection.
What Should You Do About the P1243 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application. Because P1243 is manufacturer-specific, identifying whether it relates to a secondary fuel pump, a fuel injector, or a turbo bypass valve is mandatory.
Follow the applicable manufacturer diagnostic steps to test the relevant system and components. Once the root cause is confirmed, complete the necessary repairs and verify that the system operates correctly and the code does not return.
