EEC-IV Error Code 52

[DPDISXR4Ti]

I thought this was worthy of it's own topic. I consistently get an error code of 52 - Power Steering Pressure Switch Open, and this is with two different original Merkur Scorpio PCM's, 8GHB and 8GHC. Here's where it gets weird... There is no power steering pressure switch on the Scorpio.

Has anyone else gotten a 52? I've never heard of this being brought up before.

[brokencase]

How are you pulling codes? Are you using a digital readout code reader?

[brokencase]

Here is what I think. I am assuming you are reading with a digital code reader.

The EECIV connector has many pins. In most cases for different models of the same vintage, some pins are devoted to specific function and are common across the different models. Pin 24 is the PSPS input for Tempo, Taurus etc. So even though the Scorpio has no power steering pressure switch the actual input is still present on the Scorpio EECIV.

The power steering pressure switch is a "grounding switch". That means it pulls the pin 24 low when the pressure reached.

I think your pin 24 is being pulled low and there is a code in the Scorpio EECIV that is essentially saying "Hey! the power steering switch is closed and we are not supposed to have one."

If you look at page 34-36 of the Scorpio EVTM you will see that pin 24 is not used on the Scorpio. But what is near it? Pin 25 is the only thing close and that is for the ACT sensor. You were also getting ACT error code right?

Why is your pin 24 low? Could be an adjacent short, corrosion, etc. Keep in mind this could be a problem inside the EECIV module itself or on the connector and possibly the harness. Here is what I would do. Pull the EECIV and put you DMM in continuity test mode and put one probe on pin 24 and one probe on 25. If the meter indicates continuity between those pins then your problem is inside the EECIV. Also check continuity between pin 24 and case ground or any ground pin on the connector. Otherwise do the same test on the EECIV connector in the car.

So now it is all starting to make sense I guess. Except for one thing. Why doesn't the Scorpio have a power steering pressure switch?
Just about every other Ford model of this vintage does. The purpose for the pressure switch is so that the EECIV can compensate engine idle when the driver turns the wheel and the power steering load pulls the engine speed down.

[brokencase]

I want to give you some rational for my above conclusion. It's an embedded software thing.

You might assume that in 1988 there was separate EECIV source code for ever model vehicle. That is not really the how things work.

What they had was a big blob of code that was "The EECIV code base". A new model comes along (like the Scorpio) and someone gets assigned the task of configuring the code for the Scorpio. That person takes a copy of the generic "The EECIV code base".

In the "The EECIV code base" is a big configuration file (or files). There are these conditional compiles, flags and constants. Things like HAS_MULTIPORT_INJECTION or HAS_POWER_STEERING_PRESSURE_SWITCH or HAS_TWO_O2_SENSORS, etc... There are constants for the engine displacement and the size of the injectors..etc..

So this person assigned the Scorpio project has to go through all these items and make the Scorpio specific configuration file(s).
The person then compiles the "The EECIV code base" + "Scorpio configuration files" and when its done out comes the binary that get programmed into the EECIV.

Now, the code base does evolve and new features are added and bugs are fixed. But the only model specific thing are the configuration file(s).

With this approach bugfixes and improvements made for Scorpio will automatically get propagated to related vehicles like Ranger and Bronco (and vis versa). In addition, more general strategies get propagated to all models. It's just too difficult to manage separate source codes for each vehicle.

So what happens when HAS_POWER_STEERING_PRESSURE_SWITCH = FALSE? Well there is handling code that has to do something when the the switch closes. If the car is supposed to have the this sensor then it does what it has to do (in this case bump the idle slightly). But if HAS_POWER_STEERING_PRESSURE_SWITCH = FALSE I'll bet someone had the foresight to say "Issue code 52" since we are not supposes to have one.

I'll bet most "switch type sensors" would all be handled like this. The thing is that the Scorpio is kind of unique with respect to this since most other models have all the sensors the Scorpio has ...and then some.

[brokencase]

A good modern day analogy to the configuration that I discussed is Marlin. Marlin is the controller code that is used in a lot of low end 3d printers.

The 3d printers come in all different shapes and sizes. Some have automatic bed leveling, other have extra sensors to detect different things like if the filament runs out, some have different types of thermal sensors...some have heated beds...other do not...etc...

But there is just one code base for Marlin and the code is configured for different printers....as discussed here...
https://marlinfw.org/docs/configuration ... ation.html

EECIV code was configured in a similar manner.

[DPDISXR4Ti]

How are you pulling codes? Are you using a digital readout code reader?

Yes, Rotunda STAR tester. So no chance that I mis-counted "beeps".

[DPDISXR4Ti]

If you look at page 34-36 of the Scorpio EVTM you will see that pin 24 is not used on the Scorpio. But what is near it? Pin 25 is the only thing close and that is for the ACT sensor. You were also getting ACT error code right?

Why is your pin 24 low? Could be an adjacent short, corrosion, etc. Keep in mind this could be a problem inside the EECIV module itself or on the connector and possibly the harness.

Thanks for giving this some thought Dean. Indeed one of the codes that keeps popping up is for the ACT, but not always. The code 52 seems to always re-appear (it's there any time I check).

The code 52 has occurred across two different PCM's (with different calibration codes), so I think we can eliminate an internal issue with the PCM as the root cause.

[brokencase]

I would still pull the eeciv and check with a meter to see if pin 24 is pulled to ground....then do the same on the connector on the car.

If it is not in either case then I don't know how code 52 could be occurring.