2016 Honda Accord Touring P177A and P1174 Diagnostic Guide

You’ve got a transmission code (P177A: Transmission Fluid Pressure Sensor Circuit Range/Performance) and an engine code (P1174: Fuel System too Lean or Cylinder Imbalance). Most likely, you’re dealing with two separate issues, but if both showed up at once, a wiring or ground problem could link them.

Most likely culprits

• Transmission fluid pressure sensor — Common failure point for P177A, especially if fluid is dirty or sensor wiring is damaged.
• Fuel injector — P1174 often means one injector isn’t delivering properly, causing imbalance or lean condition.
• Wiring harness/ground issue — If both codes appeared together, shared wiring or ground faults can trigger multiple unrelated codes.

How to narrow it down

1. Scan for freeze-frame and live data — Check when each code set and what conditions triggered them. If both set at the same time, suspect wiring/ground.
2. Inspect transmission fluid — If fluid is burnt, dirty, or low, it can cause sensor issues. If clean and level, move on.
3. Check transmission fluid pressure sensor readings — With scan tool, monitor sensor output. If stuck, erratic, or out of range, sensor is likely bad.
4. Check for wiring damage — Inspect harnesses to both the transmission sensor and injectors. Look for corrosion, pinched wires, or bad grounds.
5. Cylinder balance test — Use scan tool or manual method to see if one cylinder is running lean or misfiring. If so, swap injectors to see if fault follows.
6. Injector flow test — If balance test points to one cylinder, check injector flow. Replace if weak.
7. Clear codes and road test — After any fix, clear codes and drive. If codes return, recheck wiring and sensor.

Possible parts (if needed)

• Transmission fluid pressure sensor
• Fuel injector (if cylinder imbalance confirmed)

A few questions

• Did both codes set at the same time, or did one show up first?
• Any recent work or fluid changes on the transmission or engine?
• Is the car showing any driveability symptoms (harsh shifting, rough idle, hesitation)?

Let me know those answers and I’ll get more specific. If you’re not comfortable with wiring checks or injector swaps, this is a job for a pro.