Hey everyone!

Got a quick ? for anyone with knowledge about the PCM. Here's the scoop:

Bought a cool code reader to get my error codes. The thing can't read from the PCM due to no connectivity. Reader works on other cars fine. Checked the pins on the DLC (data link connector) and no power! A mechanic friend said it was on the the same circuit as my cigarette lighter - which shorted out about 6 years back when the ashtray cut the wires and blew the fuse. I fixed it way back when but re-checked the fuse and the lighter works.

I pulled the 60 pin connector from the PCM and did a pinout check to the pins on the DLC....all fine! Continuity good. Also the engine all of a sudden started idling at 1100rpm.....disconnected the intake bypass valve on the throttle body and it went to normal. Tested voltage to bypass valve (should be 10.5 volts) and it was 12.2 volts! The valve resistance was spot-on at 10 ohms (between 7 and 12 normal).

So....the bypass valve is okay. The cig lighter works and fuse is okay. Wiring harness is okay to the data link connector. The intake/oxygen bypass valve is getting more voltage than it should from the PCM.
So, here's my question to you all:

Based on this analysis and considering the short of the cigarette lighter which shares it's circuit with only one other thing - the PCM.....isn't it safe to say I need a new PCM??

I'm shopping at RockAuto.com right now but would appreciate anyone shedding any more light on this for me.

Thanks guys!! Ya'll rock!
Big Tim

 

I'm not positive on this but I'm pretty sure the ECM/PCM is not powered by the same fuse as the cig. lighter. Do you just have a high Idle condition? Have you got an early model 95 or late model OBD1 or OBD2?

 

Hey Fan....

I apologize.....I did not mean to infer the PCM is powered by the cigarette lighter circuit, but rather, that the Data Link Connector circuit in the PCM is on the same circuit as the lighter....so when the lighter shorted, it smoked that circuit, ergo...no voltage to DLC pins (no code reader capability) and the wires all pinout test fine. The PCM has power as the truck runs but I meant the DLC circuit has to be fried as there is no voltage to it, therefore it doesn't work. RockAuto has re manufactured PCMs for about $130 so I think I'll go ahead and eliminate the doubts anyway but let me know your thoughts & thanks!

 

Have you tried pulling codes with a jumper lead? just trying to help

 

Can you explain what to jump? If you mean with a tester light on the DLC to count flashes....no, as it would not work since there is no power to any of the DLC pins. It has to be the PCM, doesn't it?

 

Does the truck run? If the truck runs, the PCM is WORKING. Whether or not its working properly is what needs to be tested. And 99 times out of 100 its something OTHER than the PCM. The power feed to the EEC-IV relay comes from Fuse "I" in the engine-bay fuse block.

The ONLY power at the DLC is the power feed to the fuel pump and if the truck runs, then there is nothing wrong with the power feed to the fuel pump. (I'm not going to explain that one.)

PINK/LT.GREEN is the STI (Self Test Initiation) port.
PINK/LT.BLUE is DATA negative (-) NOT GROUND!
GREY/RED is signal return to the PCM.
TAN/ORANGE is DATA positive (+) NOT BATTERY VOLTAGE!
LT.BLUE/ORANGE is the power feed to the fuel pump relay ONLY!

A jumper between the STI (PINK/LT.GREEN) and signal return (GREY/RED) terminals will allow you to see Codes flash out via the "Check Engine Light". Of course a previously warmed engine and the key in the RUN position are also necessary.

 

Most likely your contacts on your DLC are corroded, Iv'e found the best thing for this is a points file (you may need to grind it narrower) then use a corrosion inhibitor on the contacts. I'm assuming your getting a "Vehicle Not Responding" message. (This Is Just For Future Reference) But as far as the jumper, If you look at the plug with the taper up (like a house) the two top slots, The right one will jump to the single wire plug, that's it. JUST REMEMBER IT'S THE TWO TERMINAL SIDE OF THE LARGE PLUG (TAPER FACING UP) RIGHT CONTACT. IF YOUR UNSURE DO NOT ATTEMPT! WRONG CONNECTIONS WILL DAMAGE YOUR ECM!

 

Most aftermarket service manuals give accurate diagrams as to how to obtain Codes using the jumper wire method. If you are unsure, consult one before moving forward.

 

Hey guys!!

Thanks for the fast replies. Yes, the code reader is an AutoXray Codescout 2500 ODBI & OBDII reader. It works perfectly on other cars.



The cable connector diagram for the EEC-IV Data Link Connector (DLC) is as follows:


The error is a "no communication" error from the CodeScout, but it works perfectly on other vehicles. I should have (at least) SOME voltage on pins 2 or 3....and at least 12 volts on pin 6. Alas....nothing on any of them.

From ALLDATA Online :
PURPOSE
The data link connector provides an input and output path to the Powertrain Control Module (PCM ). This allows for the following functions:

PCM Serial Data
Through the use of a scan tool information concerning sensor input values and PCM outputs can be directly accessed.

Diagnostic Trouble Codes
Diagnostic trouble codes may be retrieved or cleared with the use of a scan tool or manually with the use of a high impedance analog voltmeter.

Self-Tests
Initiation of the self-test features of the PCM can be performed manually or with the use of a scan tool.

CONSTRUCTION
The data link connector is composed of two connectors. The larger connection is a 6 terminal connector used to provide access to the PCM. The smaller connection is a single pigtail connector which is used to ground terminals on the 6 terminal connector when initiating self-tests or accessing diagnostic trouble codes.



Corrosion does not seem to be an issue here...all connectors seem clean and viable. I am still afraid the shorting of the cigarette lighter circuit which is the only other iten on the same circuit as the DLC somehow "smoked" that circuit in the PCM. I also do not agree that just because the engine runs (albeit with the Idler Air Control Valve disconnected due to an all-of-a-sudden idle of 1100 rpm & voltage levels to it from the PCM - 12.2 volts and should be 10.5)

it seems to me that all indications are the PCM is wonky...even though the thing runs. Many folks on this forum have stated experiencing bizarre issues like this and it was the PCM. I have used all the information available to me on ALLDATA Online (much much better than Chilton or Haynes - it's the resource a local and many other repair shops across the country subscribe to) and this is where I am at. Can anyone gimme something with some tangible, empirical evidence? I can't (obviously) do any tests on the DLC (even with a test light and counting the flashes) as there is no damn voltage to any of the DLC pins. The damn thing is dead...I mean deader than hell! That's why the CodeScout states "no connectivity between the reader and the vehicle" error message.

It's late...I'm frustrated and tired. Thanks again guys! I just haven't heard anything concrete to convince me it's not the PCM. But lemme know what your further thoughts are!!

Big Tim

 

Ok, this is the FIRST time I have EVER heard of or seen a Code reader that will do BOTH EEC-IV AND OBD-II. If your DLC is under the hood and looks like the one shown, you are dealing with an EEC-IV system.

 

First off, whats wrong with your Bronco other than the to much voltage you mentioned.

Second,when you say it works fine on other cars, are the other cars OBD-II or OBD-I

 

Hey guys...

Greystreak92.....yea it was a nice find and is an impressive unit. AutoXray CodeScout 2500 - bought for about $150. Lemme know if you want the website.

JDE......well, aside from the above mentioned issues, the "Ckeck Engine" light comes on intermittently, she has a hesitation (seems electronic as it is always at the same point from a stop) with the Idler Air Control Valve connected as well as the ridiculously high rpms at idle. I simply unplugged it...idle fine and no more hesitation from stop.
She doesn't downshift correctly when you gun her, she stays in 3rd, she has no giddy-up and seems tired. I am sure some of the various sensors need to be replaced like the oxygen sensor etc, but I damn sure would like to pull the codes to know exactly which ones are bad so I don't have to go and replace all of them to fix whatever is activating the Check Engine light.

The other 4 cars I read were OBD-II, not the old Ford EEC-IV but the AutoXray Code Scout came with 4 various cables for various years and makes. I did test the continuity of the EEC-IV cable pins and it seems fine so I doubt it is the cable.

My dad's mechanic in NC wants the numbers and VIN as he has some laying around and thinks he may have one for my Bronco....which would be cool and save me some $$.

We'll see what happens. Thanks again for all the help guys!!

Big Tim

 

Bronco351, you might want to read this, it's a review from Amazon: "I purchased Autoxray just last week Jan.6 2011. I have used it on 2001 Mustang GT, 2004 Lincoln Town Car and try to use it on 1994 Ford F350. The OBDII works fine for 2001 and 2004, but will not work for Ford F350 with 460 cid gas engine, with OBDI. I called the tech service for Autoxray, the company is owned by SPX Corporation in Cleveland,OH. I told the tech service guy about the problem with error that I was getting. When I connect the data cable to the Ford F350 and push read button, the screen will display "reading Failed" error message. I did this number of times and same error code. So I am on the phone with this tech person and he tells me to "check cable connections and try again" and told him that I have done trying to connect with the F350 many times and he said it must be a bad ECM. But there is nothing wrong with ECM, the truck is running fine, there is no "check engine" light on. I asked the tech person if this Autoxray 2500 is capable of reading F350, and he said yes. So today Jan. 10,2011 it does not work on Ford F350, guy on the phone was lost and did not know what to tell me to do. Another thing about this unit, it only has information up to 2003 any upgrade you must purchase data cable to computer which cost $45.00 and any data up grade will cost up to $120.00. Plan to spend additional $200.00 more after initial purchase."

In any case, if anything else has failed, try getting a loaner PCM and see if the truck works in a different way or if the reader can get the info from that one.

 

I also found this other interesting review: "Works well for both OBD I and OBD II. If your vehicle is in a transition period, say a 1995 Mustang that should be OBD I try using OBD II especially if it will take the OBD II adaptor. Tell the Scout that your car is a 1996 and everything works fine.

The Code Scout can be updated. The update is at additional cost and may not be compatable with Windows XP. I installed, updated, and then uninstalled AutoXray's software. For some reason windows did not like their software.Something about the serial interface."

Which gave me an idea... I bet you used the EEC-IV adaptor but told the reader your truck is a 95, try setting the model/year to 94 and see what happens.

This other review has great info about hardware and upgrades to your Reader, so keep it in mind: "Of the code readers out there for home use, this is far and away the most capable and easy to use; with the USB-cable version of the AutoXray EZ-PC 500 Software which you can get through Amazon for around $50 (and be sure to get that version, not the 400) Before buying the software, however, be sure to get the USB version and not the older version with a serial cable; you have to ask before buying because vendors will sell you the EZ-PC 500 with the serial cable if they have only the old one, and there is no version number from AutoXray to tell the two apart. I gave only 4 stars because it took me a lot of e-mails and phone calls with the company to find that out--not because of any problems with the reader. With the 2500 and the software you are all set to get updates to keep your reader current; you can get codes from virtually every vehicle that has code plugs; and then you can transfer the codes to your computer to chart them and keep track of them for your maintenance records. You also can reset the check engine light. If you are a professional, a scanner (at least twice as expensive) is probably more appropriate, but the 2500 with the software does everything most of us individual owners could want. Great buy via Amazon at 2/3 of current MSRP (find MSRP at the autoxray web site)."

 

FYI,
My PCM is on the way back from Ford GM ECU ECM PCM TCU Lexus Toyota Honda Acura repair used Mitsubishi after repair. Tons of good information at that site. Good to know since they are getting scarce and the numbers must match.

Bottom line, age and heat caused the failure of cheap original components. One of the three capacitors leaked, etching through five layers of clear coat. In addition to the capacitors not holding signal return voltage from sensors they ensure clean voltage to the processor chips. They replaced the capacitors with better ones and repaired the board. I'll post the results in my transmission shifting thread when I reinstall the PCM.

Might want to park with the driver's side turned away from the afternoon Summer sun.

Last year I replaced the overhead module due to capacitor failure.