Red'N'Blk95GT

I checked my trouble codes today and got several codes. I have an issue with my O2 sensors, transmission, and Electro Drive Fan circuit...These are the codes I got:

KOEO
636-Transmission oil temperature higher or lower than expected

564-Electro Drive Fan circuit fault

563-High speed Electro Drive Fan circuit fault

C
172-HEGO (HO2S) sensor fault/lean

176-HEGO (HO2S) sensor fault/always lean

639-Insufficient input from transmission speed sensor

KOER
172-HEGO (HO2S) sensor fault/lean

536-Brake on/off circuit not activated during KOER

632-Overdrive Transmission Cancel Switch/no action during self engine run test

How do I tell which O2 sensor(s) are faulty?
May the transmission issue be need of fluid flush?
And what is the Electro Drive Fan circuit failure?

Thanks in advance

88 orangepeel notch

First, welcome to the forum.

Second, I'm not familiar with the SN Mustangs as much as some guys here so I won't be much help. But I gotta ask, what issues are you having with your car? Is it run running/driving fine or horribly bad ? Is the transmission giving you problems ? And does your electric fan work at all ?

This just clarifies the issues so the smarter guys here can give accurate advice.

Also, did you clear the codes then try again ? Who knows how long some of those have been stored.

Red'N'Blk95GT

my car seems to surge when driving, either jumps in rpms or slows for no reason, seems to idle rough,and yes the fan does function, so im not sure why that code comes up. Im thinking O2 sensors need replacing but the OBD1 code reader does NOT tell you which bank or sensor is causing fault, and i am hoping a tranny fluid flush may help the surging issue and tranny codes...the trans speed sensor is brand new also...

dawson1112

Its telling you 172 HEGO bank 1 RIght side lean 176 HEGO bank 2 left side always lean.

What does that mean? Well it means that the ECM has added so much fuel to the mixture that it has reached a maximum factory threshold, it is not allowed to add more fuel allthough the 02 sensors are telling it that it needs more. This trips the DTC codes.
Most common,, Vacuum leaks , leaking header flange/manifold gasket. Faulty 02 sensors possibly, bad connections, broken wires etc. Symptoms will be excessively black/rich exhaust poor idle/drive ability may spit sputter and miss on acceleration.

Red'N'Blk95GT

Ok, so I bought new O2 sensors but am having an incredibly hard time trying to get any tool in there to remove the old ones...I rented the O2 sensor removal socket but cant get a ratchet on it...no room and BAD angle. As far as vacuum leaks i believe there may be one, but my exhaust is not black, and yes idle is rough...
Any tips on O2 removal??? Very frustrating

dawson1112

Find your vacuum leak first and see if it clears up. But getting the 02s out if Im replacing them I usually cut the wires off and use a box end wrench on em.

Red'N'Blk95GT

Ok I will try the box end wrench, im just not sure theres enough room to get wrench on it and turn, since they are mounted on an angle in manifolds, and the frame is in the way under there. Whats the best/most accurate method for locating any vacuum leaks?

dawson1112

With vacuum leaks, start with the simplest method first. A thorough visual inspection is sometimes all thats needed to find a vacuum leak. Just look for any lines that are split or just look like they are old and dry rotted at the ends.

The one place that I have found 90% of the vacuum leaks on the 5.0L engines are under the upper intake. They tend to rot out faster because they are in an area where it gets pretty hot. If you fail to find any leaks visually or by listening carefully then you best bet is to have the car smoke tested to look for leaks. You can search you-tube for DIY vacuum leak smoke test. Plenty of videos explaining it and even showing you how to make your own tester. As far as the 02 sensors go the drivers side one is not that hard to get at ,, the passenger side one is easier if you remove the starter.

Red'N'Blk95GT

so I have replaced both O2 sensors and now car idles strangely...when parked it sounds like idle goes up n down every few seconds, and when in drive with foot off brake but not applying gas pedal, car slightly lunges forward when idle goes up every few seconds...any idea why this may be happening?
thank you

88 orangepeel notch

Do a "Base Idle Reset" and post back if that helps or not.

Search this forum or Google for step by step directions.