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\'05 GT/5 Spd. Throttle Body/PCM Problem. Common/Known issue? (Sorry, kind of a long read.)

First, since this is my first post as a newly signed up forum member, let me say hello.


Now, onto the Thread Subject. Last Friday, I started up my car after work and drove roughly 15-20 minutes and stopped at a store. About 10 m inutes later, I started it backup to go home, and the Message Center had a message relating to "Failsafe Mode", but then quickly went away. I turned off the car, and grabbed my manual. The only entry in the index for Failsafe was for "Failsafe Cooling".

I checked the page listed and this is what it says:

If the engine coolant supply is depleted this feature allows the car to be driven temporarily before incremental component damage is incurred.


If the engine begins to overheat:
The engine coolant temp gauge will move to the red (hot) area. (It didn't. It was smack in the middle of the temp range.)

The "Engine coolant temp" indicator will illuminate. (It didn't come on at all.)

The "Service engine soon" indicator will illuminate. (this didn't come on either.)

If the engine reaches a preset over-temp condition the engine will automatically switch to alternating cylinder operation. Each disabled cylinder acts as an air pump and cools the engine.

When this occurs the vehicle will still operate, however:
The engine power will be limited. (No reduction in power levels.)

The A/C system will be disabled. (Worked fine. Nice and cold.)

Continued operation will increase the engine temp:
Steering and braking effort will increase. (No extra effort needed for ither.)

The engine will eveentually shut-down. (Thankfully, this never happened either.)

Once the engine temp cools the engine can be restarted. Take your vehicle to a service facility asap.

Ok, so I restarted the car and did the "System Check" and when it got to the point where it checks "Engine Coolant Temp" it came back with a result of "OK".

I went ahead and took it to my local dealer, about 10 minutes away, and told them what was happening. But they said that if it's not actually in Failsafe Mode then they wouldn't be able to do anything, because no codes would be being actively thrown. (I thought there were a certain number of codes, or time period of codes, stored in memory by the car?) He said it may have just been a faulty sensor read, due to the fact that it was at start up.

Later, when I got home and let the car cool down a little, I checked the coolant level, and was almost perfectly in the middle of the Low and High range lines.

So, all's good until this past Tuesday. It happened again, only it was while I was actually driving. So, I took it back to dealer and my service rep was talking and he mentioned that "'s probably related to the Drive By Wire set up. It sometimes has a problem working with the throttle body. We have had several come in throwing a Failsafe and they've all turned out to be Throttle Body/Drive By Wire related."

So, yesterday evening the Service Rep calls and said they either drove it around or had it running in the shop while hooked up to the scanner, just about all day, but they couldn't get it to go into Failsafe Mode. He says as this is a whole new design that's only about a year old, they haven't had much experience with it yet, so they can't just say "Oh yeah, it's this and that, etc".

But, he did say that of the ones they have worked on, it's been always been a problem with the Throttle Body mis-communicating with the PCM. The TB is either trying to open without the PCM knowing or "authorizing" it, or it's not opening when the PCM is telling it too. He said they also think that in my particular case, it's Throttle Body related, because while the car won't go into Failsafe Mode for them, it is throwing several different error codes that all relate to the Throttle Body.

So, has anyone heard of others with an 05/06 having similar issues?

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\'05 GT/5 Spd. Throttle Body/PCM Problem. Common/Known issue? (Sorry, kind of a long read.)

Please allow me to say Welcome to FM.

Now, As far as the Throttle BODY OPENING OR CLOSING... That all depends on your FOOT, NOT the PCM...

The Rates that the PCM feeds the injectors is a Direct result of your FOOT and the current driving conditions and traction.

The PCM can get a false reading of throttle Position from a faulty TPS but I cannot see the relationship between the Throttle position and the "Throttle Body Miscommunication" Unless that is what they're telling you.

I cannot see replacing the whole throttle body since it is only a shell that air passes through on it's way to the cylinder...

I can however see replacing items such as a faulty or intermittant TPS or other sensors within the throttle body sending signals to the PCM.

If the throttle body were to open without the PCM knowing it it would change the barometric pressure in the intake, thus causing the car to run rough, it would also tell the PCM through the O2 sensors that it was running too lean, because the O2 sensors would be reading more air and less fuel than optimum running requirements allow, (and the PCM would likely richen up the injection to compensate and that would cause a fluctuation in your idle and or power) then you have the various other components like the Air Flow sensor, which also sends a signal to the PCM and helps the car run smoothe, and you have many more items that all go through the PCM to attain optimum power and optimun emission reduction.

Should your O2 sensors get bad readings from the exhaust they will show up only at the time of the incident, they will only set a code when they fail fully or are out of range for a prolonged period of time.

TPS will show up "out of range" on a KOER test throughout the road test this would be constantly monitored by the testing computer, and Also would likely show up in the PCM memory as having been out of Parameters/Range.

There will be NO Throttle Body listing in the diagnostic computer's program because it is simply metal. The sensors in the TB are what matter and if there's a glitch it will show up on the PCM in 99% of the cases.

I think you should drive it until it starts to run like crap then take it to them, or until you get a code. If your gauges and fluid levels are showing good (always keep an eye on them at any rate) then drive it!


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\'05 GT/5 Spd. Throttle Body/PCM Problem. Common/Known issue? (Sorry, kind of a long read.)

just a guess- but any chance you had the pedal partly depressed before turning on the key?

theres a way to 'recalibrate' the gas pedal/throttle servo:
turn key on without starting
wait for lights to go out
depress gas pedal to floor and release
turn off key

it does make a difference- in mine the initial pedal response was much quicker- needed much less pedal in normal take off...just guessing if pcm sees 'non-zero point' at bootup it might throw that up.

edit: FE- wasnt sure if you'd seen the new 4.6 dont have a throttle linkage- just a pot on the pedal and a servo (w/tps feedback) at the TB...I really hate it. on highway at lifting throttle theres an almost exact 6 second delay before throttle fully closing/engine braking...

failsafe cooling and PCM failsafe are 2 different critters- one lets you run dry without baking the motor too bad(copied from northstar Caddy), the emissions/PCM failsafe allows limping home with a faulty sensor somewhere- partial throttle/rich/late timing to keep from leaning out and killing it.

'failsafemode' is more like the old 'check engine light' used to be- the pcm sees abnormal data from a sensor, so ignores it and runs a safe ,yet dirty, 'mapped' fuel curve so you dont need a towtruck.

Confidence: that feeling you have just before you realize the mess you've gotten yourself into...

<font size=-1>[ This Message was edited by: ford4v429 on 5/13/06 9:12am ]</font>

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34,722 Posts
\'05 GT/5 Spd. Throttle Body/PCM Problem. Common/Known issue? (Sorry, kind of a long read.)

I haven't seen the new 4.6... No throttle linkage? It's all digital if I guess correctly?

So it has a TPS on the TB and it has something like a TPS on the Foot feed to send a signal to the TPS on the TB to open and close the Intake...

Is that what you're saying?


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3,349 Posts
\'05 GT/5 Spd. Throttle Body/PCM Problem. Common/Known issue? (Sorry, kind of a long read.)

yep- drive by sucks, but the car is otherwise a blast!
I *think* they did it for 2 reasons:
1) the car scoots and could really require traction control for someone not used to this type of power from a new car(13.5 in the 1/4 aint bad for 100% stock!) and the traction control is VERY effective by slamming the throttle vs the old ignition/timing cutout type things...and its programmed to still allow a bit of squealling the tires without stumbling- however dumping the clutch with t/c on is embarassing
2) the delayed 'off' at lifting throttle allows some of the extremely high vacuum situations time to clear out- this helps a lot with emissions I guess by sucking less oil, and keeping some flow thru the cats...supposedly it exceeds the low emissions stuff greatly, still gets 26mpg highway, and runs 0-60 in 4.9/13.5 in the 1/4...Ford really hit the nail on the head with this little bugger.

dont think its 100% digital- I know the heater controls are analog feedback-into eventually digital pcm-already been into wiring diagrams to figure out better blend control- in 'foot' heat, still blows 90% at defrosters- they apparently all work this way...a couple properly sized resistors or a pot should fix it- maybe even a pot/thermistor for 'climate control' type thermostat? I think the TPS on my lincoln was analog too- only had 3 wires I think...

the bad thing, its got 'break me' written all over it- servo on the TB, another servo on the 'charge motion plates'(like a set of butterflies inside the intake to divert low intake flows at injectors for better swirl/atomization at the injector), some kind of servo thing on each camshaft to advance/retard timing(might just be oil pressure solenoids- not sure)...anyway, gotta say for such a tiny motor man does it run- and makes some of the most beautiful noise Ive ever heard
Not simple, but man does it get the job done.

<font size=-1>[ This Message was edited by: ford4v429 on 5/13/06 10:11am ]</font>
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