Cel 173 & 176 | Ford Explorer - Ford Ranger Forums - Serious Explorations

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Cel 173 & 176


New Member
May 31, 2014
Reaction score
Year, Model & Trim Level
1994 Ford Ranger
I have a 1994 Ford Ranger 4.0L with codes 173 & 176. (System rich bank 1, and system lean bank 2.) Both O2 sensors bad? Bad fuel pressure regulator? Plugs and wires bad? All of the above? The truck cuts out at low speeds, but when I floor it, it will pick up power big time. Where should I go first?


Used to be a road here.
Elite Explorer
November 21, 2013
Reaction score
City, State
Phoenix, AZ.
Year, Model & Trim Level
1994 Explorer Limited

These codes have two fault states depending on the type of test run.

176 KOER = insufficient TP change during No o2 check.
While 176 KOEO indicates always lean.

If your CEL is on and you pull the codes after the drive cycle you would have 176 "lean"

If you are getting both lean and rich faults; the fuel delivery is jumping around.

If that's the case I'd start with looking at FPR, and for leaky injectors.

The TPS can cause erratic injector action, and is most likely the cause.

So, very first thing is to replace that $50 headache.