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EAC fail + OBD no link


Alan18
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Good day to Everyone,

After cleaning the Mass Air Flow with spray, I heard a slight (starter-like clunk) when starting. Later that day, EAC fail appears without major engine problems (perhaps slight hesitation). At home, plug in OBD2 and "no link" appears, so check all fuses and relays and still no link. I noticed that when I turn key on, the "check engine light" and "glow plug light" do not appear, but I never noticed them before either. Is this normal, and what can be the OBD connection problem?

 So at this point, I cannot get a diagnostic code.The EAC fail is intermittent, but only after warm, and the engine starts and runs.

Thanks in Advance.

Fusion 1.4 TDCI

 

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No idea why no link with OBD reader. I assume the reader you have did work on this car before? maybe reader just gone wrong.

http://www.fordwiki.co.uk/index.php/Instrument_Cluster_Self-Diagnostic_Mode

This shows how to test the instrument cluster lights, do glowplug and engine management lights work on this test.

If I had EAC fail I would check plug connectors on throttle body and throttle pedal.  Throttle pedal can also be tested with a multimeter for resistance.  They have two circuits in there for safety reasons. The ECU checks that both of the potentiometer circuits are giving the same reading at the throttle position.  If one is giving a resistance  different from the other the ECU will detect that.  I am not sure exactly what the car does at that point, if it uses the lower setting to control the throttle (so it does not accelerate when you did not intend that) or if goes into limp mode or raise the  EAC fail message etc. 

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Isetta, thanks for the cluster link, I'll work on that later (yes the OBD worked before).

I know where the pedal switch is, but pardon me, I'm not sure where the throttle body is. Is it under the MAF, on the engine at around the camshaft level, or in the back near the EGR valve? I've been curious about its location before, but now i really have to find it.And actually, now that you brought up the TPS, I did notice the engine does not accelerate as quickly as before--so this must be it.

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Doesn't look like there is a throttle body according to Haynes and parts suppliers. Will try to test the throttle pedal with ohm meter and see if resistance changes smoothly.

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Yes, all good. Intermittent EAC FAIL without difference in temperature or distance, but driveability not affected. Is it always the Throttle Position Sensor?

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actually, thinking about it, do diesels have a throttle body?  aren't they free breathing without a flap and only petrol has the flap on an electric motor. On diesels the throttle pedal tells ECU to shove extra diesel out of the injectors only. Not sure, I am confusing myself now. Hopefully someone else can clarify 

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Correct, my diesel does not have flap on intake, so ECU and pedal do the work--this I found out just now.

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Yes, the pump and injectors control fuel delivery.

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7 hours ago, isetta said:

do diesels have a throttle body?  aren't they free breathing without a flap and only petrol has the flap on an electric motor.

Yes (sometimes) & Yes!

The 1.6TDCI & 2.0TDCI (usually) do have throttle valves on the inlet, mainly to help the EGR to work, I think. Also they act as anti-shudder valves at turn off. But the 1.8TDCI has no throttle, and all diesels are normally free breathing, with little or no inlet manifold vacuum. This inlet vacuum (or pressure below atmospheric to be more pedantically accurate!) wastes quite a lot of energy, and hence fuel, on a conventional petrol engine.

On 1/27/2018 at 11:48 AM, Alan18 said:

At home, plug in OBD2 and "no link" appears,

A 2002 Diesel did not need to be OBD2 compliant, that only came in in about 2005 for diesel (about 2000 for petrol).

Forscan with a suitable ELM327 adapter that has the full range of diagnostic interface standards, should be able to communicate with a pre-OBD2 Ford. It works with the Mk1 Focus. The DTC codes, if you can read them, may be more informative than the in car display.

I suspect all the lights should come on at ignition on. The usual reason why they do not is that some naughty dealer has tampered with them!

 

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But the OBD2 reader worked before even though engine and glow plug light do not normally display. From the previous owner, there once was a major dealer electrical overhaul a long time ago, so that might be the light problem.  I really need a reader to get to the bottom of this so will test my OBD on another vehicle and if broken buy the ELM327.

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23 hours ago, Alan18 said:

Is it always the Throttle Position Sensor?

The word throttle is used confusingly these days. Once upon a time, the accelerator was linked to throttle valve by a bowden cable, so they were one system, really. That is long gone now, almost all accelerator pedals (APP) are electronic, sending signals to the ECU. The ECU then controls fuel, and, if they exist, any throttle valves on the engine according to some software map or strategy.

EAC refers to electronic accelerator. According to one writer who sounds like he knows what he is talking about (a 2003 Fiesta in this case):

"The EAC light/warning is supposed to be exclusively for faults with the fly-by-wire electronic throttle.
On a Fiesta, it's usually the pedal sensor, which comes complete with pedal for £21 and takes 3 minutes to fit. [Cleaning it's plug often works too.] "

The EAC usually has two outputs, one to the Instrument Cluster (IC), one to the ECU. The ECU reads the IC signal over the car's bus system. This same bus is used for the diagnostic (OBD or pre-OBD) link. So there could be a link there.

If the bus is CAN, then there should be 60 ohms (ignition off) between pins 6 & 14 in the diagnostic connector. A reading other than this would be due to a break in the link between IC & ECU. But I am not sure what bus system was used on the 2003 Fiesta/Fusion.

 

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Sorry for the delay, work.......

I just opened and cleaned the pedal sensor, but still EAC. There are six pins to the plug; with two pairs of small tabs that slide up their own two circuits making a connection. Perhaps as isetta mentioned, they two pairs compare the readings. Am enclosing pics of the potentiometer set-up, and unfortunately it is not 21euro but more like 170e; too bad I cannot just buy the actual circuit board half, as that is all that could be wrong, considering the tabs have continuity and the pedal spring-action is fine. Without a spec sheet, I cannot check resistance, so am still uncertain if this is the culprit. Which brings me to my other problem of not having an OBD2 connect.

I was able to connect to other vehicle and OBD worked, so there is definitely a link to my faulty " check engine " light. What i have read is that without the "check engine" light on, the OBD will not work, and fuses are usually the culprit. The last time i used the meter was when i put in new injector seals and an EAC came up upon repair completion. But my meter worked and just disconnecting the battery was the trick. So if all this time I am mistaking about never having the "check engine " light working and perhaps it was working the previous time, pardon me as this is something that one takes for granted and not notice.

I checked both "check engine" fuses and relay, all are good. When i pulled one fuse, the 2 lights in question that do not normally work (engine and glow plugs), worked--but dash lights were blinking also. It's so difficult to work without the OBD diagnosis, and it looks like there are only two possibilities: The pedal or the ECU/PCM (computer). I hope not the ECU as even if i buy it from a junkyard, i hear that it has to be reprogrammed!

 

20180129_180601[1].jpg

20180129_180625[1].jpg

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5 hours ago, Alan18 said:

Without a spec sheet, I cannot check resistance,

You can still do a fairly thorough resistance check. The element end to end resistances should be sensible values (1k to 10k, I would guess), not change if the pcb is gently stressed (to a level it would see in use), and probably very similar.

As you can probably see, one element is pins 2 to 6 (numbered 1-6 from the left as seen in the photo), the other element is 3 to 5.

The pick-up elements (wiper or middle connection on a normal pot) are pins 1 & 4. With the rotating wiper part in place, there should be a stable resistance from the metal of each wiper to the pins 1 or 4. I would expect this to be appreciably lower than the element resistances above. The resistivity of the ink used to form each part of the pot can be different without any different appearance. Again it should be stable, and similar between the two.

This unit is clearly adjusted, by the laser trimmed resistance elements you can see, so that the output from each part will closely match. So any mismatch would be an error. Now you can see the connection arrangements, back-probing the connector with the unit connected and fitted to the car, and powered up (ignition on), will show the voltages from each element, and check that both parts are receiving power (probaly about 5v, but may be 12v), and ground.

I have never come across a case where the MIL (check engine light) needs to be on for the diagnostic system to make contact. Certainly not in my car. Diagnostics can also monitor sensors etc, with no fault present. So I am bemused by the MIL & glow-plug lights being off all the time except when a fuse is removed! I take it the engine still runs ok, obeys the accelerator pedal, and instruments like rev counter work?

But with the only working diagnostic pointing to the EAC, I would investigate this further. From the care with which that unit has been factory adjusted, I would say that a 2nd hand EAC should work without programming, if you can get one cheaply.

The pcb also looks a bit contaminated. A clean with a soft, small brush would do no harm, possibly even a gentle clean with IPA or similar electronic cleaning agent. (I would not use WD40 or contact cleaner, though some people use them for everything!).

.

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Tdci-Peter thanks for hanging on with my issue. You seem to know a lot about this unit, have you repaired one?

I cleaned the unit with electrical cleaner but to no avail. I get the EAC, but the only engine difference so far is a slight lag after shifting; all instruments work.

In order to test the unit in the car--not too much space, I will have to buy some small clips for each pin, otherwise my Ohm tester probe will touch the adjoining pin.

I agree that it is time to look for a used pedal, and the search has started. I will follow up, most likely on the weekend.

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1 hour ago, Alan18 said:

You seem to know a lot about this unit, have you repaired one?

Nope, never seen one before laugh.png.

It is all from your very detailed photo of the pcb, plus a bit of general electronics knowledge.

I have found before that trying to get wiring info for the Fiesta / Fusion cars of that generation is very hard. (I am assuming it is the Fiesta based Fusion, Ford seem to have used the name for other models also!). So I do not know how info about rpm, engine temp and all the engine lights gets to the IC (Instrument Cluster). On later cars it is all via the same CAN bus that is used by the diagnostic system, and it also carries the APP (Accelerator Pedal Position) from IC to ECU. Hence my question about RPM & drivability. If this CAN bus existed but was broken, it could affect a lot of things, not just the APP & Diagnostics.

Is there evidence of the normal 12v power at the diagnostic socket? It is usually on pin 16, with grounds on pins 4 & 5.

At the moment, without any real symptoms, no wiring diagram and no diagnostics, it is not an easy one!

 

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  • 2 weeks later...

Hello Everyone,

I do not want to leave you all uncertain of my Fusion's state, so here is the temporary latest:

I ordered the pedal from eBay, but they sent a slightly different version (pedal straight, hitting the cabin wall), so am in the process of getting another one. I will definitely follow-up, as you are all helpful, and it is the "right thing".

Thanks

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  • 2 weeks later...

Not fixed yet, as the new (used) accelerator pedal did not change the EAC fail.

I did get to clean the PCM harness contacts and check the data link plug for hot, ground and it has 60 Ohms between CAN (as per Peter); the check engine light and glow plug light are good with the self test mode ( as per Isseta), but these do not light when key on.

 There is a known issue with this problem for Fusions and Fiestas: 76/2003 or 75/2007 Ford TSI (Technical service Information)

Should a customer express concern about loss of power and that the electronic accelerator control failure message is displayed in the instrument cluster, the probable cause is a contact corrosion on both, the pins within the TP sensor and the fuel charging wiring harness electrical connector, causing the following diagnostic trouble codes (DTCs) to be stored in the Powertrain Control Module (PCM).

Any other source of fault needs to be eliminated before the PCM is the culprit::

  1. throttle body
  2. wiring from the throttle body to the PCM
  3. acceleration sensor
  4. wiring from the acceleration sensor to the PCM
  5. all connectors between throttle valve, PCM and acceleration sensor

My problem is compounded by the addition of the instrument lights failure--perhaps it is the PCM as I did not see any direct link from the instrument lights and the ignition switch from the Ford wiring diagram. So without a reader to hone in on any trouble codes, it must go to the Ford shop for a diagnosis, but I wonder if they even can get a reading?

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  • 1 month later...

Solved-Case Closed

After four months of research and uncertainty, the EAC Fail has finally been repaired. It was the most obvious part, but it was difficult to figure out due to this badly designed Ford program. Now I know that the EAC does not have to be literally understood as the accelerator components, BUT as anything that effects the acceleration. For me it was the MAF, even though I did not receive an OBD error on this the first time, but the third! Another inconsistency that perplexes the mechanic is that the error codes could be a false-positive or a false negative--in other words, one cannot rely on the OBD fully either, as I have replaced the accelerator pedal and EGR without resolution.

I have spent much time scouring the web for answers to this dilemma, and what I discovered is that a) there are many unhappy car owners who never solve the problem; b) there are a myriad of solutions to the ones that are repaired (i.e. EGR, ECM, MAF, better fuel...); c) the ECM is a major culprit; d) Ford's Technical Bulletin on faulty connectors-at least to me-seems like a guess in the wind.

In summary, it's a bit of "guess and replace" while using all your mechanical wits.

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