551 - IAS - Secondary Problem

[dantheman68]

So I'll start from the begining...

During the sensor test of a KOEO EEC test, my car displayed code 551, which was the IAS, also known as secondaries. Originally I didnt know what was happening, but the vaccum was constantly being applied to the butterflies, leaving them constantly closed.

Then I found that somone replaced the IAS sensor, including the plug that connects it to the 'puter with a different type of vaccum controller, not a secondary controller. So i figured i'd buy the correct part, i bought it from a member here on the forum, and got a tail of the wiring, so i could splice the correct connector on... i installed it and it felt much more powerful above 4k

i figured all is well...

I ran the KOEO again... got that 551 code again... now the car wont close the secondaries, im thinking there's a discontinuity or something in the wiring, and assuming the controller is working. i soldered the conector on, so im sure its hooked up correctly, and i did use electrical solder...

i guess im wondering what i should look at now... is there a certain voltage that the computer sends the IAS to tell it when its below 4K? so i know if it has continuity?

i am also currently at school, and do not have my car with me so i wont be able to "go out" and check it... but if anyone has some voltage #'s or can get them for me... it would be greatly appreciated, as well as any other ideas... ive hit a wall so to speak

 

[hawkeye18]

Make sure you routed all the vacuum lines correctly when you installed the IMRC runner. Both the vacuum canister (you do have one, right?) and the controller can only be wired one way. A light green/pink wire supplies power from the PCM (pin 32), I would assume this goes to either +5 or +12 volts when the RPMs goes to 4K. The other wire goes to the CCRM, pin 24. The vacuum reservoir (black can thingy) is wired correctly if the port that you can suck air through is hooked up to the intake. It's a one-way valve. IIRC, the other port is hooked up to the bottom port of the controller. Try reversing these, though, that might be your problem.

It's easy to check continuity of the two wires to make sure they're not opened somewhere. Other than that, the vacuum obviously worked before so I'd check for mixed-up vacuum lines. It's way easier than you'd think. If none of that helps, the PCM might be bad, but that happens so very rarely...

Pin 24 of the CCRM is the very left bottom pin as you look into the connector face of the harness. Pin 32 of the PCM is... um, not used? according to the '95 EVTM. Page 24-1 says the wire goes to pin 32, but the C191 pinout chart says 32 is empty. Anyway, pin 32 is two pins to the right of that center retaining bolt in the middle row as you look at the harness connector.

I hope this helps. You'll be amazed at how different it is when the runners are closed below 3.5K!

 

[dantheman68]

the vaccum port goes like this =

Intake Vac ---> 1 way canister (which has vaccum) ---> Bottom port on IMRC then Top Port ---> butterflies

so they should be right... i looked at my buddy's sho to get this

i should probably look at the voltages, where can i find the "pins" and what connections are you talking about? is this on the PCM? whats the CCRM? is it the same thing?

 

[Rockledge]

i guess im wondering what i should look at now... is there a certain voltage that the computer sends the IAS to tell it when its below 4K? so i know if it has continuity?

i am also currently at school, and do not have my car with me so i wont be able to "go out" and check it... but if anyone has some voltage #'s or can get them for me... it would be greatly appreciated, as well as any other ideas... ive hit a wall so to speak

IMRC circuit operation is described in this thread:

http://www.shoforum.com/showthread.php?p=620791

 

[dantheman68]

WOW, amazing thats exactly what I needed... amazing that i couldnt find that in my search... probably because there isnt secondary written in it...

Props to both of you!

i'll save this link and see what happens when i get home!

 

[dantheman68]

*****BUMP***** UPDATE

I finnally got around to checking this out, and heres what i have (secondaries still do not close below 4K) (open all the time)

the vaccum lines are all connected correctly, and even if they werent it wouldnt give a computer code, like i am still recieving...

I have ~14 volts on the red wire, and about 5 volts on the green wire the secondary controller itself has 99ohms of resistance

i am truly confused as to what the next step is and exactly whats going on with all of these voltages... from what ive read and understand, it seems like the computer is sending the correct voltages to the correct wires at the correct time

 

[projectSHO89]

... probably because there isnt secondary written in it...
quote]

Probably because you should have searched for the plural....


99 ohms for the IMRC solenoid coil sounds ridiculously high....and +5 V on the low side of the coil just isn't right....


Steve

 

[dantheman68]

well, im now wondering if i measured it correctly... i know about electronics and how to measure, but i dont know if i took my readings at the correct spots. to record the voltage, i disconnected the electrical connecter from the secondaries, and then took readings (off of the connector, which was disconnected from the secondary controller), should i have measured the voltage while the connector was still connected to the controller?

i hope im not horrilbly confusing

 

[dantheman68]

just an update for others refrence...


after swapping out the ECU, the secondaries are now fully operational... i couldnt believe it... i guess im lucky that it was only the secondaries that the ECU decided to crap out on

 

[Rockledge]

just an update for others refrence...

after swapping out the ECU, the secondaries are now fully operational... i couldnt believe it... i guess im lucky that it was only the secondaries that the ECU decided to crap out on

Interesting. The PCM is at the bottom of list of possible causes. But it's on the list nonetheless, and your situation demonstrates why.