Symptoms
Symptoms of a P2193 engine code may include:
- Malfunction Indicator Lamp (MIL) illuminated
- Lack of power
- Occasional misfires
- Poor fuel economy
Causes
Possible causes for this code being set include:
- Faulty Air/Fuel Ratio Sensor/Oxygen Sensor (AFR/O2)
- Faulty Mass Air Flow (MAF) Sensor
- Rarely – Faulty Powertrain Control Module (PCM)
Diagnostic and Repair Procedures
A good starting point is always to check the Technical Service Bulletins (TSBs) for your specific vehicle. Your issue might be a known problem with a published fix from the manufacturer, which can save you time and money during diagnosis.
First, note if there are any other Diagnostic Trouble Codes. If any are related to the fuel/fuel system, diagnose those first. Misdiagnosis is known to occur if a technician diagnoses this code before thoroughly diagnosing and clearing any fuel system-related codes. Ensure there are no intake or exhaust leaks. An intake leak, or vacuum leak, causes the engine to idle roughly. An exhaust leak makes the engine appear to be running lean to the AFR/O2 sensor.
Once located, visually inspect the connectors and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Disconnect the connectors and carefully inspect the terminals (the metal parts) inside. Check if they appear corroded, burnt, or possibly greenish compared to the normal metallic color you’re used to seeing. You can get electrical contact cleaner at any auto parts store if terminal cleaning is needed. If not available, find 91% isopropyl alcohol and a soft plastic-bristled brush to clean them. Then, let them air dry, get some dielectric silicone compound (the same type used for bulb sockets and spark plug wires), and apply a small amount where the terminals make contact.
If you have a scan tool, clear the Diagnostic Trouble Codes from memory and see if this code returns. If it doesn’t, the connections were likely your issue.
If the code returns, we’ll need to test the voltage signal from the MAF sensor to the PCM. Monitor the MAF sensor voltage on your scan tool. If a scan tool is not available, test the signal from the MAF sensor with a Digital Volt-Ohm Meter (DVOM). With the sensor connected, attach the red voltmeter lead to the MAF sensor signal wire and the black voltmeter lead to ground. Start the engine and monitor the MAF sensor input. As engine RPM increases, the MAF sensor signal should increase. Check the manufacturer’s specifications, as there may be a chart indicating the expected voltage at a given RPM. If it fails this test, replace the MAF sensor and retest.
If the previous tests pass and the code is still present, monitor the Air/Fuel Ratio Sensor/Oxygen Sensor (AFR/O2). If it continuously indicates the engine is running lean, locate all possible causes that could result in a lean condition. These include:
- Intake or exhaust leaks
- Fuel system, including fuel pressure regulator/fuel pressure
- Fuel pressure sensor
- Fuel injectors
- Bank 2 O2 sensor after the catalytic converter
- EVAP system, including the canister purge valve
If the AFR/O2 sensor indicates the engine is running normally or even rich, a faulty PCM may be suspected, but only after all other potential issues have been ruled out.
Again, it cannot be overemphasized that all other codes should be diagnosed before this one, as issues causing other codes to set can also trigger this code.