Technical Description of OBD-II Trouble Code
Incorrect Fuel Composition
What is the meaning of this code?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles (Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
A stored code P0169 indicates that the powertrain control module (PCM) has detected a voltage signal from the fuel composition sensor/fuel temperature sensor that indicates an unusually high level of contaminants or ethanol in the fuel supply. In flex fuel vehicles, high concentrations of ethanol may not cause any issues, but levels exceeding eighty-five percent would be considered unacceptable.
The fuel composition sensor is typically integrated into a single housing with the fuel temperature sensor. Although it looks like a fuel filter, it is actually a small computerized device designed to provide the PCM with accurate analysis of fuel composition and temperature.
As fuel flows through the inline sensor, it is electronically analyzed to determine the presence of ethanol, water, and other contaminants that are not fuel-related. The fuel composition sensor not only analyzes the composition of the fuel, but also its temperature. This information is sent to the PCM as an electrical signal, which reflects the contaminants present and the temperature of the fuel. Fuel contamination is analyzed based on the ratio of contaminants to fuel.
This analysis generates a voltage signature in the fuel composition/temperature sensor, which is sent to the PCM as square waveforms of voltage. The frequency of the waveform patterns varies depending on the degree of fuel contamination. A higher frequency indicates a greater degree of contamination. The fuel composition sensor specifically analyzes the amount of ethanol present in the fuel, independent of other contaminants.
If the PCM detects an input signal from the fuel composition sensor indicating that fuel contamination exceeds a programmed limit, a P0169 code will be stored and a malfunction indicator lamp (MIL) may illuminate. In some vehicles, multiple ignition cycles with a failure may be required for the MIL to illuminate.
Code Severity & Symptoms
A stored code P0169 should be considered severe because fuel composition is crucial for calculating fuel delivery strategy in flex fuel vehicles. Contaminated fuel can also cause damage to fuel delivery and internal engine components.
Symptoms of this code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is to check for technical service bulletins (TSB) specific to your vehicle. There may be a known issue with a known fix provided by the manufacturer, which can save time and money during diagnosis.
To diagnose a code P0169, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), an oscilloscope, an infrared thermometer, and a vehicle information source (such as All Data DIY). A diagnostic scanner with an integrated DVOM and a portable oscilloscope should suffice.
Begin by visually inspecting all related wiring harnesses and connectors to increase the chances of a successful diagnosis.
Using the DVOM and your vehicle information source, test the reference voltage at the fuel composition sensor connector. If there is no reference voltage, use the DVOM to test the corresponding circuits at the PCM connector. If a reference voltage signal is identified at the PCM connector, repair the open circuit between the fuel composition sensor and the PCM. Note: Before testing circuit resistance with the DVOM, disconnect all related controllers. If no reference voltage is present at the PCM connector, suspect a faulty PCM or a programming error.
If the reference and ground are present at the fuel composition sensor connector, use the oscilloscope to observe live data in the form of waveform patterns. Connect the test leads to the signal and ground circuits and observe the display screen. Use the infrared thermometer to measure the actual fuel temperature and compare it with the temperature reflected by the waveform patterns on the oscilloscope. If the fuel temperature shown on the oscilloscope does not match the reading from the infrared thermometer, suspect a defective fuel temperature sensor.
Additional diagnostic notes:
