← Back to list

1997 Ford F-150 Heater Malfunction (DTC PO161) - Bank 2 Sensor 2 Fix & Misfire at Plugs 6 and 8

Model: 1997 Ford P/U Fault Code: P0171 Posted: 2008-03-20 15:43

I own a 1997 Ford F-150 with a 4.6L engine, currently at 242,000 miles. The vehicle is displaying DTC PO161, indicating a heater malfunction in Bank 2, Sensor 2. I recently replaced the downstream oxygen sensor located just after the catalytic converter, but the code returned after only about five miles of driving. Additionally, I performed a recent spark plug replacement and confirmed that the spark plug wires were installed three years ago and are in good condition. The vehicle is now showing misfire errors at plugs #6 and #8. I replaced the coil pack on the left side (Bank 2), which resolved the misfire for Plug #8, but the error reappeared for Plug #6. We have thoroughly inspected all spark plug wire connections to ensure they are secure. Could the issue be related to the catalytic converter itself? Should I replace the upstream oxygen sensor even though no error code is present? While this might be considered a maintenance action, could it resolve the heater malfunction and misfire symptoms? I would greatly appreciate any expert advice as I am currently at a loss on how to proceed with this issue.

Related fault codes
P0171
Comments (6)
Anonymous 2008-03-20 20:59

Check for vacuum leaks—sometimes these can interfere with heater performance. Also, are the ignition wires showing signs of arcing? If there were no misfire codes before the tune-up, it's possible that one or more spark plugs or connections were damaged during installation or became loose.

Anonymous 2008-03-22 20:45

Andre, This issue is similar to a thread I found: http://f150online.com/forums/showthread.php?t=315189 I hope this helps. Gary P.S. Jeff—here's a relevant plug for your situation! This case involved aftermarket parts causing the problem, which was resolved by switching back to OEM components.

Anonymous 2008-03-31 09:01

After replacing both downstream oxygen sensors with Motorcraft OEM parts, the check engine light and misfire codes disappeared. The solution worked well for me.

Anonymous 2008-03-31 09:02

Thank you so much for sharing your resolution, Andre!

Anonymous 2008-03-31 09:37

Great to hear! I've found that aftermarket oxygen sensors—especially those from brands like Bosch—often have a poor reliability record. Unless the price is drastically lower, it's best to stick with OEM parts for underhood components such as O2 sensors. While alternators and filters are generally reliable, most other after-market parts tend to fail prematurely when cross-referenced with original equipment specifications.

Anonymous 2008-04-02 16:55

Nice update, Andre! Thanks for confirming the resolution.