What this code means
P0175 means the PCM may be seeing bank two running richer than expected.
What the vehicle may do
- The MIL may be illuminated.
- Stop/start may be disabled if the vehicle is equipped with that feature.
- The vehicle may have driveability or fuel system symptoms.
Possible fault areas
- Possible fuel delivery or fuel quality concern.
- Possible leaking injector or purge solenoid concern.
- Possible intake restriction, exhaust restriction, or engine mechanical concern.
- Possible MAP sensor, oxygen sensor, oxygen sensor wiring, connector, or PCM concern.
Diagnostic path
Opening context
On this Ram 1500 with the 5.7 Hemi, P0175 points to the PCM seeing bank two run richer than expected. The driver may notice the MIL on, and if the truck has stop/start, that feature may be disabled while the code is active. A rich condition like this can come from fuel delivery problems, a leaking purge path, air or exhaust restriction, engine mechanical issues, sensor wiring, oxygen sensor feedback, MAP sensor input, poor connections, or, less often, the PCM. Start with the basic system checks before getting deep into testing.
Monitor gate and failure logic
Before chasing the fault, make sure you can reproduce the operating conditions. This monitor is looking for a fuel-control problem severe enough that emissions can reach 1.5 times any of the standards. It runs with the engine in closed loop fuel control, battery voltage above 11.0 volts, barometric pressure greater than 75 kPa, ambient temperature above -7°C (20°F), fuel level greater than 12%, and altitude below 2590.8 m (8500 ft.). The PCM sets the fault when the combined short-term and long-term fuel corrections drop below a calibrated threshold, generally 67%, with 100% being nominal. After 30 seconds of fail time, the diagnostic fails.
Confirm the code is current
First, use the scan tool to read codes in all ECUs and record the data. Save a full scan report and the related captured data for comparison later. Clear the codes, turn the ignition off for a minimum of 10.0 seconds, then turn it back on. Operate the vehicle under the same type of conditions that set P0175, then read codes again. If P0175 does not return, treat it as an intermittent condition. If it does return, continue with the rich-condition path.
Check for other fuel or air concerns first
Next, look at the recorded codes. If other active or pending fuel-system or air-handling concerns are present, handle those first. This fault can involve an oxygen sensor or wiring, but on this path it is more likely to be driven by a mechanical, fuel, or air-handling issue, especially if the truck also has driveability symptoms. If there are no related active or pending concerns, move on to the exhaust check.
Check exhaust restriction
Start the engine and check for good exhaust flow at the tailpipe. Then visually inspect the exhaust system for damage that could create a restriction. If you find a restriction or related damage, make the appropriate repair, then verify the repair and confirm the code stays gone. If no exhaust problem is found, continue to MAP sensor operation.
Check MAP sensor operation
Check MAP sensor operation using the MAP sensor operation test. If that test finds a problem, repair as needed and verify the repair. If MAP operation checks out, continue to the purge solenoid test.
Test purge solenoid sealing
Turn the ignition off and disconnect the hoses at the purge solenoid. With a hand vacuum pump, apply 5.0 in. Hg. to the ENGINE side of the purge solenoid. The solenoid should hold vacuum for a minimum of 15 seconds. If it holds, reconnect the vacuum hoses before continuing, then go to the fuel delivery check. If it does not hold, verify good pin-to-terminal contact at the evap purge solenoid and PCM connectors. If the connectors check out and no connector issue is found, replace the purge solenoid, then verify the repair and confirm P0175 stays gone.
Check fuel delivery
Now check the fuel delivery system using the fuel delivery test. If that test finds a problem, make the appropriate repair and verify the repair. If fuel delivery checks out, continue into engine mechanical checks.
Check engine mechanical condition
Check the mechanical and fuel-quality areas that can drive a rich fault. Make sure the air induction system is not restricted, valve timing and compression are within specification, and the fuel is not contaminated. If an injector is suspected of leaking or having an abnormal spray pattern, remove the fuel rail with the injectors intact, energize the fuel pump to maintain rail pressure, and look for fuel leakage before actuating the suspect injector. Then actuate the suspect injector or injectors with the scan tool, inspect the spray pattern, and compare it with the others. If a mechanical or injector-related problem is found, repair as needed and verify the repair. If no mechanical problem is found, move on to upstream oxygen sensor wiring.
Check upstream oxygen sensor wiring
For the upstream oxygen sensor wiring check, disconnect the upstream O2 sensor connector and the PCM C2 connector. Do not probe the PCM harness connectors directly, because that can damage the terminals and create poor terminal-to-pin contact. Use the GPEC Diagnostic Adapter 10436 if probing is needed at the PCM side. Check the upstream O2 sensor circuits between the sensor connector and PCM C2 for a short to ground, and for an open or high resistance. If you find a wiring problem, repair it and verify the repair. If the wiring checks out, continue to oxygen sensor operation.
Check oxygen sensor operation
Check oxygen sensor operation using the oxygen sensor operation test. If that test finds a problem, repair as needed and verify the repair. If oxygen sensor operation checks out, go to the final connection inspection.
Inspect related PCM and component connections
At this point, inspect the related PCM and component connections carefully. Perform any applicable service bulletins. Disconnect the PCM connectors, any related in-line connectors if equipped, and the related component connectors. Look for improper connector installation, damaged locks, corrosion, water intrusion, weather seal damage, bent terminals, overheating from a poor connection, terminals pushed back in the cavity, spread terminals, and poor terminal tension. Repair any conditions you find. Then reconnect the PCM, in-line, and component connectors, making sure everything is fully seated and locked. Clear the codes, operate the vehicle under the monitor conditions again, and read codes. If P0175 does not return, the wiring or poor connection issue has been repaired. If P0175 does return after this path is complete, replace and program the PCM, then verify the repair and confirm the code stays gone.
Closing takeaway
The key on P0175 is not to jump straight to an oxygen sensor. Confirm the code is current, handle other fuel or air concerns first, then work through exhaust flow, MAP input, purge sealing, fuel delivery, engine mechanical condition, O2 wiring, O2 operation, and connection integrity in order. For more diagnostic training, visit stepdiagnostics.com.
Final check
P0175 is often best approached by confirming the fault first, then separating fuel, air, mechanical, sensor, wiring, and connection causes in order.
For more guided automotive diagnostics, visit STEP Diagnostics.
