Why do I keep getting p0172 and p0175 codes?
What complicates getting to the bottom of what’s causing these two codes to pop up, is that they don’t accuse one specific component as being bad. For example, most folks mistakenly believe that these codes point to a failed oxygen sensor and that’s the first thing that gets replaced (among many) that do not solve the issue.
What does it mean when fuel trim is p0172?
Ideally, the Long Term Fuel Trim should be close to 1 to 2 percent. When a code P0172 is set, it means that the Fuel Trim is anywhere from -15 percent to as low as -30 percent compensated. When this happens, the computer knows that there is an improper condition in the control of the Fuel System.
What happens when the O2 sensor is stuck?
If the O2 sensor stays stuck at a Rich Condition (anything above 0.500 millivolts) for too long, the PCM will try to reduce the amount of fuel to change the O2 sensors values. Since the PCM is reducing fuel, the LT Fuel Trim (Long Term Fuel Trim) values will go into their maximum negative Value of -20%.
What does the PCM do when the engine is running?
When the engine is running, the PCM is constantly adjusting the amount of fuel it’s injecting. These adjustments are called Short Term (ST) Fuel Trim and Long Term (LT) Fuel Trim. And you and I are able to see the values that are generated on a scan tool with Live Data capability. Each engine bank is adjusted separately from one another.
What does fault code p0172 and p0175 mean?
P0172/P0175 Diagnostic Theory for Shops and Technicians. When a vehicle has the fault code P0172 and or P0175, it means that computer can no longer automatically adjust the mixture between air and fuel. Code P0172 applies to Bank 1 and P0175 applies to Bank 2.
When the engine is running, the PCM is constantly adjusting the amount of fuel it’s injecting. These adjustments are called Short Term (ST) Fuel Trim and Long Term (LT) Fuel Trim. And you and I are able to see the values that are generated on a scan tool with Live Data capability. Each engine bank is adjusted separately from one another.
If the O2 sensor stays stuck at a Rich Condition (anything above 0.500 millivolts) for too long, the PCM will try to reduce the amount of fuel to change the O2 sensors values. Since the PCM is reducing fuel, the LT Fuel Trim (Long Term Fuel Trim) values will go into their maximum negative Value of -20%.
What causes a PCM to report a rich condition?
An inaccurate Coolant Temperature or Air Temperature Sensor can cause a rich condition because they will report that the engine is still cold, which will cause the PCM to keep the mixture rich long after the engine is at proper operating temperature.