glemmers

I've been helping a friend get his '87 TII running again. After replacing the leaky injectors, we are able to get the car to run, but only if we keep above 2,000 rpm. Checking the error codes, we got an 02 (AFM).

So, we started by ohming out the AFM per the FSM. The car has a new (rebuilt?) unit that was installed about a year ago; the last time the car ran. When checking the two E2 pins (ref. 4B-59 of the FSM), we get 180 ohms across the two. If the FSM wiring schematic is correct, their should be 0 ohms across both E2's. Does anyone know if this is correct? The other measuremetns are close, but depending on which E2 we use, the values vary by 100+ ohms.

Next we ohmed out the harness grounds through the ECU (E2 for the AFM connector) and got 0.1 ohms. We then tried to measure Vs at the connector with the ignition on and got 0.06 V. not the 4.0 stated in the FSM. Gaining acess to the ECU, we also got .06 Volts at pin 2E (the AFM Vs). As a sanity check, I checked the TPS Vr at 2G and got 1.0 V with teh ignition on. So, I believe the ECU circuit for the AFM is kaput.

Now the impotant questions: can the ECU be easily repaired? Has anyone else had this problem before?

Thanks in advance,

Glenn

HAILERS

I think your doing something not quite right. In section 2B, the idea is to disconnect the afm and put it on a bench. Then touch the pin that goes to E1 and the other lead to E2. The meter on ohms, you should get something like .1 to .3 ohms. Shove the vane in the afm open and the meter reads open or no continuity.

If the afm is connected up, and the ECU has all its plugs on and the key is to ON, not START and not idling, the meter if set on ohms and the meters positve lead on 2E (shoved up the back of the plug), and the negative meter lead is on a good ground on the chassis, then the meter if set on DCvolts should read approx 2.5vdc to 3.5 vdc.

For checking the ground for the AFM you need to remove the plug from the AFM. Then put the neg lead on a good chassis ground and the positive lead on the BLACK wire and then the brown wire with a black stripe. each wire seperatly. With the meter on ohms you should read somewhere around .1 to .5 ohms depending on the resistance in the meter leads etc.

Make sense??????? a

glemmers

HAILERS,

Everything you state makes sense, and is exactly how we tested the AFM, wiring harness, and ECU.

We did check the AFM disconnected. And I realize that the FSM does not specifically state to ohm across both E2 pins on the AFM, but we checked it because the other tests in the FSM were slightly off, depending on which E2 pin we choose to run the tests. If you look at the AFM internal wiring diagram, both E2 pins are ganged as grounds. The problem is we measured 180 ohm across the two E2 pins.

We also checked pin 2E (AFM Vs) at the ECU with the AFM connector plugged in and the ignition key on. Results were .06 V.

Aso, we checked the AFM grounds just as you state. The AFM is grounded throught the ECU. Checking the mating connector for the AFM, (which the E2 pins engage into) we got .01 ohms back to the negative post on the battery.

So, have you ever heard of the ECU internal AFM Vs circuit failing? Can it be fixed? Do you know anyone that repairs ECU's?

Thanks for your reply,

Glenn

HAILERS

OOps. I was not paying attention. No. I get .001ohm on the two E's if reading just across the pins on the afm.

Tell you what, if you take the plug off the afm, and check voltage on the Brown/white wire on the plug, do you get approx 4-5 volts?

No, I never had a bad afm circuit, myself.

It sounds like the grounds are good, so you must be missing the 4-5 v on the brown wire with the black stripe (later cars might have just pure black instead of brown/black).

If you don't have the 4-5 volts on the brown/white wire, then pull the plug off the pressure/boost sensor and see if there is 4-5 vdc on its brown/white wire. If you don't have the 4-5 volts on either brown/white wire, then the voltge reference signal out of pin 2A has gone kaput (probably not the case since you got 1 volt out of the tps).

HAILERS

When reading the afm by itself, did you get the 200-400 ohms when checking E2 to Vs and then E2 to Vref?????????

If your reading 180 ohms across the two E's, it sounds like there is a problem indeed. Take the black cover off. You have to cut around the edges of the black cover with a razor. Its just RTV holding it in place.

With the cover off, IF I remember right, you can see the solder connections on the afm's plug. Maybe, just maybe you be able to see something amiss with the two E's connections,.

We read on occasion how someone will not know how to disconnect the afm's plug and will unscrew the jack on the afm from the afm and screw the pooch, instead o just pulling the connector off the afm.

I'd still check the brown/white wire for the 4-5volts, but the 180ohms is plain wrong and it must be a wiring problem internal. I'll bet you can fix it when the black cover is off. I'm talking about the very large, D shaped cover. About 3 inches by 3 inches. NOT the black electrical jack with the pins.

2Lucky2tha7

iTrader: (3)

MAKE SURE that the AFM unit you put on the car is DEFINITELY the right one!! If the AFM is from a Turbo and it's put on a non-turbo, that'll cause problems. Same goes if it is a non-turbo afm and put on a turbo car. They both look the same.

HAILERS

I currently have a turboii afm on my 86 n/a. Sorry, just had to throw that in there. It's a N332 where a N326 should be. Reason???? Screwed up my n/a afm when I took the cover off and randomly played with the spring/vane etc. NOT knocking what you stated, just couldn't pass up making a remark.

HAILERS

This:

HAILERS

Again

HAILERS

Items Inside The Afm:

glemmers

Hailers, thanks much. We'll pull open the AFM and check out the E2 grounds. I'll also check the boost sensor for power. I apreciate all your input.

Glenn

HAILERS

Sorry, my goof. The brown/white wire should be close to 4vdc. Mine is 3.9vdc. So don't go looking for that extra volt to make it 5.

BlaCkPlaGUE

Make sure that you seal it back up with caulking glue afterwards. The last thing you want is dust and **** to get back in there if it already has, it should be perfectly clean inside the afm area.