'94 code 212 mystery IDM Resistor ??? - Ford Bronco Forum
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post #1 of 35 (permalink) Old 07-18-2008, 12:48 PM Thread Starter
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'94 code 212 mystery IDM Resistor ???

Having occasional no-start problems. Last year about this time (probably heat related) same thing, I replaced the PIP (whole dist actually), the coil, ignition wires, and TFI (ICM) which is the remote mounted kind. It was time for those parts anyway, and it solved the problem.

Now a year later, the same no-start, and throwing code 212 (IDM input failure).

After a long search, I did the Tech Service Bulletin on the harness, opened up the looms on the harness between the PCM and ignition parts... no issues.

It's throwing the 212 code still, and I can't find the IDM resistor. There's some debate whether it even exists on later models in the threads about this. I really suspect the TFI is failing sporadically in the heat, but want to find that damn resistor first. The TFI checks out ok on the bench.

Anyone get any clarity on the mysterious 22k ohm resistor?

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post #2 of 35 (permalink) Old 07-18-2008, 01:31 PM
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I've done a LOT of research on this in the past few months. It turns out that indeed, Ford turned to a CCD (computer-controlled dwell) ignition module sometime between 1993 and 1995. I only found this out because, like you, I got the code 212 along with some ignition problems. Well, that and Steve83 and I had slight disagreement; I'd incorrectly assumed the parts catalogs to be correct, whereas his recollection was based upon Ford's schematics. Now I only trust the OE schematics and OE part numbers. I've bugged the local Ford dealer's parts people to DEATH over some stupid things like this.

I'll let you read this Standard Tech Tips article to give you a better idea of the difference, how to tell which you have, and what to do about it:

Quote:
Originally Posted by Standard Motor Corporation
FORD- IDM FAULT CODES AFTER MODULE REPLACEMENT

If you run across a Ford vehicle that has an IDM (Ignition Diagnostic Monitor) fault code, this tip may be helpful.

The TFI module (Thick Film Integration, which refers to the type of internal circuitry used in this module) has been used on the EEC-IV system since its inception. There are two different module types, and, even though they may look alike, they are not interchangeable.

One type is referred to as the "Push Start" type, while the other is called the "CCD" (Computer Controlled Dwell) type. The "Push Start" module gets its name from the 4th pin on the module connector, which is a start signal inputfrom the starting system. When the module receives this 12 volt input, it increases or "Pushes" he ignition coil dwell for maximum coil output for easier starting. The "CCD" module does not use a start signal input, but does rely upon the ECM Spout input to control ignition coil primary dwell. By the way, ECM Spout controls ignition timing on both module systems.

Under normal running conditions, the "Push Start" module starts the ignition coil primary dwell time about 3.5 milliseconds before then next anticipated coil firing. At this point the module is waiting to see the Spout signal voltage change from low to high. When this happens, current flow to the coil is stopped, which will result in the coil firing. If the time is longer than 3.5 milliseconds, the module will reduce the primary current to prevent the coil from overheating, since it cannot anticipate the next coil firing. The "CCD" module relies solely on the ECM Spout input to change ignition coil primary dwell time. On this system, the trailing edge of the Spout wave will start the primary cycle, while the leading edge of the next wave will end it, resulting in the coil firing. The time in between signals is the dwell.

Both modules are used in systems where they may be mounted on the distributor, or, they may be remotely mounted away from the distributor (commonly called "Closed Bowl" versions). Usually, the "Push Start" modules are gray in color, while the "CCD" modules are black.

IDM is a feedback signal generated by the ignition system and is monitored at pin #4 of the ECM. Its purpose is to diagnose missed ignition primary pulses at the time the ECM commands the Spout signal to fire the coil. Since it is used solely for diagnostic purposes, if this circuit is not operating properly, it will not affect vehicle driveability.

Both "Push Start" and "CCD" systems produce an "IDM" signal, however, they do it in different ways. The "Push Start" system uses an external 22K ohm resistor (22,000 ohms) that is usually taped to the wiring harness that is connected to the negative terminal of the ignition coil. [On our trucks, it is usually located in the harness between the engine and the driver's side fender] This resistor is used to lower the voltage of the Tach signal being supplied to pin #4 of the ECM.

This external resistor is not used on the CCD system since it is part of the internal circuitry of the module, which produces the IDM signal. So, the IDM signal travels from pin #4 of the module directly to pin #4 of the ECM.


Oddly enough, the "Start" pin on the "Push Start" module is the same pin as the IDM pin on the "CCD" module. While the connectors are identical, interchanging the modules may or may not create a driveability problem, while tripping a fault code of #18, or # 212 (IDM code). These are problems consistent with interchanging one type module in place of the other.

Identifying the correct module for your vehicle can be accomplished in a number of ways. First, always refer to the correct application in the Engine Management catalog. If that information is not available, check the wiring of the vehicle. If pin # 4 of the module gets a start signal (which should be battery voltage) from the starter circuit, it's a "Push Start" system. On the other hand, if pin #4 of the module is wired directly to pin #4 of the ECM, then it's a CCD system (refer to diagram #5).
So, if your original TFI ignition module was black, the auto parts store more than likely sold you the wrong one. This is because ALMOST ALL of the parts stores' catalogs are WRONG. They all list the "push-start" type of module, NOT the correct CCD. I guess asking whether the original module was black or gray was too much trouble for the shitbags writing the catalogs; instead, they just plagiarized someone else's erred work.

Like the article says, you'll have to do some checking if you don't remember whether your original module was black or gray. Check the voltage on the TFI connector's #4 pin during cranking. A steady +12V signal during cranking means it's the older push-start (as outlined in the article). If it goes directly to the #4 pin on the PCM, it's a CCD.

Here's the F'ed up part: try asking for a CCD TFI ignition module in a parts store.

Not to worry. The Wells part number is F139, Niehoff's is FF413, BWD is CBE40, and Standard's number is LX-241, if that helps. Even Motorcraft's catalog was superseded by the push-start module; I guess Ford doesn't particularly care whether your diagnostic systems are working properly or not.

An alternative is to look up the ignition module for a 1994-1995 Mustang GT. These should also have the same, remote-mounted CCD modules the later Broncos should have. In this application, the Motorcraft part number is DY1077, with OE numbers: {#5U2Z-12A297-D, DY679, or F1PZ-12A297-A}.

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post #3 of 35 (permalink) Old 07-18-2008, 02:16 PM Thread Starter
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Outstanding. Thank you.

My original TFI is black, and the one they sold me last year is grey. The rest of that Tech Tip concurs with what I saw in the harness... connections to pin 4 on the EEC, no 22k resistor, and slightly different wiring pattern than Haynes shows sans that resistor.

I've traced and verified all the wires from the EEC to all ignition components, so I'm pretty sure the no-start is from heat (it's like 100 degrees here right now) and a faulty TIF. I might attribute the wrong TIF module I got last year to some very subtle drive problems, and of course the 212 code.

Great post, thanks again. That one definitely goes in the files.

P.S. may not be news to others, but I hate printing stuff like this in IE, it ****les the formatting. Been using Mozilla Firefox, and you can adjust the print parameters and print out something like the above post perfectly.... too cool

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post #4 of 35 (permalink) Old 07-18-2008, 02:46 PM
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NP.

Just another FYI: fault in the spark plug wires and/or ignition coil can cause the ignition module to fail. All of the coil's inductive energy has to go somewhere, and if there's an open in the secondary circuit, you can bet it's going to push uphill.

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post #5 of 35 (permalink) Old 07-18-2008, 04:10 PM
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I spent two days looking for the resistor, could not find it. My EEC is also black, the parts person gave me a gray one, had more problems with the gray one. My problem was no PIP signal, new dizzy solved the problem. THANK YOU !!! for this info!!!
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post #6 of 35 (permalink) Old 07-18-2008, 08:47 PM Thread Starter
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Just got back from Zone, we tested the old (somewhat functional) and new (suspect) TFIs. Both failed, though it took more than one test run to get the newer to fail. Of course the only one they had was the incorrect Grey one. Picked it up anyway to have a spare, and will find the lifetime warranty paper for the other one I bought last year.

Should be back on the road tomorrow.

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post #7 of 35 (permalink) Old 10-07-2008, 08:12 PM
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I have the same 212 code popping up. But my trouble is not the ICM I've triede both of them. Hers whats happening: After the engine heats up if I turn it off sometimes it wont start back up just turns over, Fuel pressure is good, Timing is right, cap and rotor are good, plugs and wires are good, I've replaced every sensor I can find, the coil is new, the started is new and Ive checked all my electrical connections and everything looks good. IS there anything else I can do? driving me crazy and broke :(. Please help!
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post #8 of 35 (permalink) Old 10-07-2008, 08:41 PM
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You can't have a code 212 on a 1988 Bronco. You have two-digit codes in that model year. If you were seeing a DTC 21, which is what I think you really saw, then that indicates that the ECT is out of self-test limits.

Stop throwing sensors at it. You're wasting an enormous amount of time and money doing that, and it may in fact make the existing problems worse (you run the risk of damaging other components when you replace sensors). I keep telling people here: DIAGNOSE, TEST, SERVICE. In that order and no other.

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post #9 of 35 (permalink) Old 10-07-2008, 08:49 PM
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Sorry man I also have a 95 I just added it. ITs the 95 that has the issue I have put the code reader on and its a 212 code. My bad
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post #10 of 35 (permalink) Old 10-07-2008, 09:10 PM
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Ah, gotcha. No biggie.

In that case, I'd start looking for a faulty PIP. There's a diagnostic procedure...umm....somewhere around here or in the Haynes manual.

Honestly, the best diagnostic I've found for a bad PIP is to watch the tachometer on the dashboard. If there's no PIP, there's no tach signal. No tach signal, no tachometer reading during cranking.

EDIT: I was thinking of DTC 211. DOH! The definition for 212 is "Loss of IDM input to EEC or SPOUT circuit grounded." In that case, of course check for a grounded spOUT first, and then check out the TSB in Steve83's SuperMotors.net page regarding this condition. In essence, the shielding around the ignition harness likes to cut into the wiring sometimes. That's one important item to check. Another is the connection between the IDM line (pin 4? on the PCM) and the ignition control module. An open or faulty connection here can trip that code as well. I don't have my Ford tech service CD handy right now, but there are other things to check.

You tried both a black ignition module (one for, say, a 1994-5 Mustang GT) and a gray one, with no change? Did you clear the DTCs after changing modules?

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post #11 of 35 (permalink) Old 10-07-2008, 10:57 PM
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Yeah I have a black BWD CBE40 that was for a musatang and a napa grey one that says its for a 95 bronco. I'll the shielding after work tomorrow. thnx. I'll post an update as soon as I'm finished.
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post #12 of 35 (permalink) Old 10-07-2008, 11:09 PM
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Hey Sig, good on ya for that exemplary work. I've been doing my job for about ten years now, and even I didn't know about the different modules. Thank you.
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post #13 of 35 (permalink) Old 10-07-2008, 11:30 PM
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post #14 of 35 (permalink) Old 10-08-2008, 02:29 PM
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One thing I am confused on, does the black CCM module that is dizzy mounted have the same three prongs that fit up into the dizzy as the gray push start one does? I looked up the part numbers Sig provides and they show the TFI module to be black with no three connector spades. Fireguy posted and it looks like you can get both the the push start and the CCM in either a dizzy mounted version that has the 3 spades or the remote version that does not. Can someone please clarify for me. Thanks. I am just trying to figure out which version this WAY1 computer I have needs. Trying to rewire before putting EFI harness back in and having to tear it apart again once I crank it up and get code 212.
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post #15 of 35 (permalink) Old 10-08-2008, 03:02 PM
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The CCD ignition modules were used only in remote-mount applications, IIRC. There MAY have been an application, like an Escort or Taurus, that had a CCD ignition module mounted on the distributor, but I really don't know as I haven't looked into it. That WAY1 was used exclusively with a remote-mounted ignition module, though.

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post #16 of 35 (permalink) Old 10-08-2008, 04:07 PM
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The ECC doesn't care if the TFI is remote or dist mount.
Trust me I've got a black TFI mounted to my distributor
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post #17 of 35 (permalink) Old 10-08-2008, 04:32 PM
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Great, thanks for the help.
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post #18 of 35 (permalink) Old 10-08-2008, 07:08 PM
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after following all the wiring with a flash light I wasnt able to find any shorts or crimps in the wire. under the shielding everything looked really good clean almost new. Any other ideas?
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post #19 of 35 (permalink) Old 10-08-2008, 09:59 PM
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Test the PIP.

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post #20 of 35 (permalink) Old 10-09-2008, 12:39 AM
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On the Grey TFI module, I tore into my harness to do the rewire for use with the Black module. I found that wrapped in a black sheath with 22 Ohm stamped on the outside, two wires, both Brown/Yellow on one side, one goes to the TFI plug, the other goes to ground at the Coil. On the other side, I had a Brown/Yellow and a White/Red (dashed), which I figure one goes to pin 4 on the EEC, the other to the Tach. I had a hard time tearing into that shealth cover, but inside, it looks to me like there is a resitor on each line, one on to the EEC wire and the other on the tach wire. Fireguy's diagram does not show a resistor on the tach wire. I printed out my schematic from Alldata and sure enough, a 1990 shows the wire coming off the TFI plug, and a restor on the EEC line and the tach line as well. Since the Black TFI module I will be using does the resistance internally, I know that I do not need the resistor for the wire going to the EEC. Question is, do I need to leave the resistor in place going to the tach?
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