1998 Ford Expedition Transmission Issues: P0174, P0155, P0135, P1136 - After Engine Replacement with 4.6L Motor
I recently replaced the engine in my 1998 Ford Expedition (245,000 miles) after a rod bearing failure occurred two weeks ago. The new engine is a 4.6L from a 1997 Lincoln Town Car with only 76,000 miles. I am confident that all electrical connections were properly installed, and both transmission fluid and engine oil are at full levels. During the removal of the old engine, the torque converter was kept connected to the flywheel — so I believe no damage occurred to the transmission itself. All fuses have been checked and appear functional. However, my truck will not move in any gears except reverse. The fault codes appearing on the OBD2 scanner are P0174, P0155, P0135, and P1131. I’ve confirmed that the knock sensor was not fully torqued in place — but I understand this does not affect transmission operation. My question is: could any oxygen sensor, wiring harness, or electronic component related to the engine management system be improperly connected or faulty? Specifically, do these O2-related codes (P0174, P0155, P0135) indicate a transmission issue or are they more likely related to engine sensors? I would greatly appreciate any insight into whether there’s a sensor or wiring connection that might be missing or damaged — especially one that could cause the truck to fail in all gears except reverse. Any help would be much appreciated!
All of those codes (P0174, P0155, P0135, P1131) are oxygen sensor or related system faults — they typically do not directly cause transmission failure or no-shift issues. However, it's important to confirm the exact transmission model and whether your truck has 4WD, as this can affect drivetrain behavior. Make sure your OBD2 scanner is capable of reading all codes, especially those above P0999 (such as P1131), which may indicate deeper system errors. A key point: could a wiring harness have been pinched or unplugged during engine replacement? Check the transmission connector — specifically look for 12V power on the red wire (positive supply). Use a test lamp to verify continuity and voltage at the harness terminals. If there's no power, that may indicate an electrical issue affecting transmission control signals.