'94 4WD codes 536, 172 & 173

[bikerchick4God]

Hey ya'll. I need some direction on these codes:

536 No power to BOO switch
172 System too rich Bank 1
173 Fuel trim malfunction

Are the three related? Or just the 172 & 173... My mileage has deteriorated since purchase in Sept. I travel in work and it is critical I have her running well.
The used car dealer has been NO help at all since day one so I am on my own in getting her up to peak. Till I am off work for several week beginning in Dec, I cannot take her in for any length of time. I dont know if the 196k miles are orig or if eng and/or trans are replaced/rebuilt. I couldnt see any yellow date lettering but I dont have a lift either.
Back to the sensors... do I replace them both? And how difficult is it for me to do.
Some other helpful ?? info: cruise hasn't worked, speedo dances 65 mph+ 5/10 mph, temp gauge normally sits at far left & she loses some power at a slight incline. Brake lights were out when vehicle was sold to me. Dealer fixed this but haven't had her scanned since to see if BOO code was removed.

Thanks all and happy up-coming holidays
nancy, in daytona beach

luvin my explorer

 

[MrShorty]

Is the 536 a KOEO, KOER, or continuous memory (CM) code? KOER 536 is quite common, usually because the operator forgot to press the brake at the appropriate time during the KOER test. If a KOEO or CM code, a 536 indicates an electrical fault in the Brake On/Off (BOO) circuit.

Are the 172 and 173 KOER or CM codes? My code list shows that both of those codes refer to the right/rear O2 sensor. 172 indicates lean, and a 173 indicates rich -- an interesting contradiction. Whichever test they were from, were there equivalent codes in the other test? If CM codes only (passed KOER), then I would suggest clearing the CM codes, driving the truck, and seeing which code(s) come back. If you haven't run the KEOR test yet, then run the KOER test.

 

[bikerchick4God]

thanks

I will pass this on to my mechanic who may or may not appreciate the advice LOL. All I know is the tech scanned the codes. The engine light only comes on after I've been on the highway for 8+ miles and then intermittently as I drive high mphs. Tis why I never saw it when test driving the truck locally
nancy

 

[bikerchick4God]

I get it!

It took me some time to figure out KEY ON ENGINE OFF ... I don't recall what the tech did but will take notice next time. I went to Autozone the other night and he couldn't scan it, all he had was an OBDII and first gen is OBDI ??. I'll be shopping for an scan tool for under $100. Anyone have one they use & recommend? I liked autotap but dont have a laptop or palm to record the scan.
Thanks and hope ya'll had a wonderful Thanksgiving.
nancy

 

[Runnin'OnEmpty]

Hi Nancy, glad you're liking your Explorer.

Those O2 codes are probably caused by a bad sensor, especially since the light comes on intermittently during highway driving. That's a typical symptom for a bad or carbon-covered O2 sensor.

Do the brake lights work now? If so, the BOO code is probably old, and can be erased for good.

 

[MrShorty]

See tests at www.dalidesign.com/hbook/eectest.html if you want to do this without a scanner or code reader.