1995 740iL IAC wont turn off/How to test for a bad DME/Tranny in limp mode (3rd)

[goinstrong]

I just picked up a nice looking 1995 740iL as a project car, but have found it to be more than expected. (Surprise!)

Here are the issues:

1. Idle Control Valve stays on with key off (hums)

2. ABS light was on: Code for rear passenger speed sensor (1F) and random scatter (40)(either just sensor or the ABS unit is bad also) I cleared them but haven't driven it since (yet)

3. Transmission is in limp mode: 3rd gear only going forward, but neutral, park and reverse work. (manual switch registers, but no difference realized if I try to shift gears manually) Will the stomp test show a code for a bad tranny?

4. Battery is marginal. I have it on a charger, and will have it tested once it is fully charged.

5. Valve cover gaskets leaking pretty significantly. I will replace and put in new plugs as well. No misfiring, but a slightly rough idle.

6. Stomp test results: 1213, which is lean/rich for more than 10 seconds. I am certain this is due to #5 above.

I ordered a new ignition switch on the outside chance that it will stop the IAC from running. Simple to eliminate.
Any thoughts on the tranny? Could a bad battery put the car into limp mode? It is the 5HP30.
Is there a simple way to test the DME?
Thanks for any input! It is greatly appreciated.
Tim

[asianvenom]

A bad battery causes many funny problems...make sure you have a good battery, clear the codes and start over and see what comes back. The rear speed sensor though is more likely be an issue, try remove and cleaning it.

Sent from my SM-G965U using Tapatalk

[Mayorchuck]

Yes, battery is often the cause for TFS. You can't really diagnose much with this car with a weak battery. It causes to many gremlins.

No 'easy' way to diagnose the DME without BMW software. How did you get the code for the wheel speed sensor? That, alone, will cause your ABS light. You can swap it with the other side to see if the code follows but that's probably your issue. Don't buy junk aftermarket sensors. They won't work.

[goinstrong]

Minor update: I pulled the ABS codes from the reader in the engine bay with my Autel scanner, and cleared those codes. I will be cleaning the wheel speed sensor today. I was able to get hold of another identical DME, and the chip from mine was swapped into it. I will be having the battery tested today since it was fully charged. I left it for a day to see if it will hold a charge.
I will update once I have a fully charged battery and the DME is installed. Thanks for the advice/encouragement!
Tim

[acspecialists]

On these cars don't mess with charging and testing too big of a risk when TS. Get a new properly sized AGM and forget about it. I am a cheap skate but on this one I don't mess around.

[rslifkin]

Given an appropriate modern-ish charger (not one of the old school transformer things that just blasts power at the battery with minimal voltage regulation) you won't hurt anything by charging the battery, even with it in the car. It won't expose the electronics to anything outside of the voltage range the alternator can be expected to put out.

[goinstrong]

Update: I put in the new DME with my chip, and now the IAC doesn't stay on. Mayorchuck, I thought I had cleared the ABS codes, but the light is still on. There are 2 different codes on the stomp test: both for the 2 O2 sensors, again related I suspect to the bad valve cover gaskets.
The battery is holding a charge, but I will be swapping in the good battery from my son's 1998 740i, because the tranny is still in safemode. It now shows up on the dash, so the old DME did have problems. I tried unplugging the ABS module to see if the tranny would work, but no luck.
I noticed a drip down underneath the tranny, so I will be verifying there is enough fluid. Fingers crossed!
The battery is slightly low (13.2-13.4), and slightly high when running (14.9-15.1), so the battery could be bad after all.
More to come after I swap the battery, verify full tranny fluid, and clean the rear wheel sensor. Thanks for all the input!
Tim

[rslifkin]

If it's cold outside, charging voltage will typically be higher (especially right after a cold start) in cold weather than in warm weather. 15-ish volts in the winter wouldn't concern me, lots of charging systems will get up there on a cold start. 13+ after the battery has been resting for a while is fine, a lot of batteries won't hold that high a resting voltage just by their nature even when healthy. Anything 12.6+ is usually fine when resting (exact target is battery dependent).

[goinstrong]

Thanks for the clarification about the charging system. I guess the battery is fine then, which is good and bad. Hoping to get the trans fluid checked tomorrow.
Tim

[goinstrong]

Today I was going to have the tranny fluid checked. I had the battery out and charging (still has a 2.5 amp draw I have yet to find). I replaced the starter switch on the outside hope that would solve the draw, but no luck. However, I started it up, backed out, and it shifted through all the gears on my way, through 5th on the freeway. But, after it was turned off and back on, it went back to failsafe mode. Fluid level is fine, and the fluid is not bad looking or smelling. It is a Green tag tranny FYI. The engine light came back on, but the stomp test didn't work for some reason. I wonder if the draw causes lower voltage, and puts the tranny in failsafe. What do you all think?
Also, while it was up on a lift, my son and I gave it a once over. The wheel sensor "box", where the 2 ends connect, is missing at the rear passenger side (the one that came up on the code) and bare wires are dangling from the "car" side. The "wheel side" connector from the sensor is full of mud. Anyone have a wiring diagram for that area? I am thinking of cleaning the sensor, and then hard wiring it to the wires from the "car" side to see if the light goes out. There are 4 wires from the "car" side, but I am not sure where the other 2 are supposed to connect. Can anyone help? Thank you all again! I have to say I was encouraged that the tranny worked, even if only for one key cycle.

[Mayorchuck]

https://www.newtis.info/tisv2/a/en/e...ection/lpGjHtq

There should be two sensors on that side. The wheel speed sensor and the brake pad wear sensor. Do you have a check brakes warning on your cluster?

https://www.newtis.info/tisv2/a/en/e...d-wear/bFx3EAH

- - - Updated - - -



- - - Updated - - -

RH rear wheel well

X377	Component connector (2-pin, grey), Wheel speed sensor, rear right
X18146	Plug connector (2-pin, black), Rear right brake pad sensor

[goinstrong]

Mayorchuck,

Thank you for responding. Yes, the dash scrolls to check brakes. Thank you for the picture. Can the the brake sensor wires coming from the car be connected together to complete a circuit without going to the brake pad sensor? That would give it continuity, correct?

Any trick to figuring out the polarity of the wheel sensor wires from the sensor so I can connect it to the 2 bare sensor wires coming from the car? I think the 2 sensor wires from the car are supposed to be green/blue with green stripe. I doubt the wires from the sensors are color coded. I haven't opened it up yet to tell, but am hoping today is the day.

Regarding the ignition switch: the one I removed had a little white plastic pin in the center. The one I put in is an empty hole. Could this be the reason the stomp test isn't working properly? I figured if the car started, the new switch was fine. Thanks for any thoughts on this everyone!
Tim

[Mayorchuck]

You can complete the circuit to take care of the brake warning. I've done it myself.

I've never owned a '95 but I know many who have to do the stomp test many times to get it to work.

Here is the best link I know of on the wheel speed sensors. I will also include a link showing the sensors with bare wires. I don't know if polarity matters or not. They are hall effect sensors so the sheath is important as well. i have taped up cracks in those wires but have never tried splicing them. I know some have had to replace those connectors from parts cars as well.

https://www.bimmerfest.com/forums/sh....php?p=4205801

http://www.bimmerboard.com/forums/posts/853273/

[goinstrong]

Thanks! I read on one of the forums that the green wire is for Pin 11 at the ABS module (early E38s and E39s), and has a negative charge, while the Blue wire with green stripes is Pin 38 and has a positive charge. I just assumed they would need to be connected to keep that polarity.

Is there any further damage I could do if I connect them "backwards"? I am concerned it might damage the ABS module...

I was thinking about finding a "car side" part of the harness with the connector, and then plugging in the sensor from the wheel to see where each wire lines up (if that is possible). Hopefully, the first connection attempt would then be the correct one!

[Mayorchuck]

If it were mine, I would pull the driver side connector off and check to see if I could pull the sheath down enough to see the wires on both side to maybe match them up. I'm sure someone here has spliced them in the past.

[goinstrong]

If it were mine, I would pull the driver side connector off and check to see if I could pull the sheath down enough to see the wires on both side to maybe match them up. I'm sure someone here has spliced them in the past.

Good idea! The colors will be different, but I bet one of them has a stripe on it. I will match it up that way and hope for the best!

[goinstrong]

Update: I read on another thread that cleaning the air temperature intake sensor solved the transmission failsafe mode. I tried it today, and it worked. The M60 has the sensor on the side of the intake manifold, so it wasn't as simple as being on the airbox, but it is sure worth a try. This tranny shifts smoothly, and has NO hesitation going into reverse.
I will be tackling the bare wire situation tomorrow or Saturday, and will report back. Thanks again and Happy Thanksgiving everyone!
Tim

[goinstrong]

Regarding the bare wires in the rear passenger wheel well, I had my son solder and then shrinkwrap the 2 brake wires together. I found a connector and box at a local wrecking yard, and that got soldered/spliced onto the bare wheel sensor wires coming from the car. The sensor plug from the wheel still had the other half of the connector in it, so the connection inside was nice and clean, and fit perfectly. I think I will have to clear the ABS code and the brake lining code for them to go away, but now the system should be up and running properly, assuming striped wires connect to striped wires!

[racer2086]

I didn't read everything, but from the initial sound of your issues I was going to suggest checking the ignition switch, because of the ABS issues and the ICV being active with key out in addition to you battery drain issues. It could also affect the transmission voltage based on each start depending upon whether the contacts make good contact or not.

Check the ignition switch first...just had ABS and airbag issues due to that in an E39. Then put your old DME back in to see if the ICV stays off.

[goinstrong]

Racer2086,

Thanks for your input and ideas! I did replace the ignition switch, but it didn't solve the ICV issue, which was there before I swapped out anything. I did the switch first, then the DME. If I connect the battery, but don't start the car, the ICV is "hot". If I start the car and turn it off, it stays off. I just swapped out a bad amplifier for a good one, and it seems like the power drain is now at normal levels. I will be verifying this tomorrow, but it looks like it is around .2-.3 milliamps IF the ICV is off. If it stays this way, there were 2 potential draws on the battery: the ICV if put in accessory mode (or when the battery is reconnected without starting the car), and the amplifier. The amplifier had been pulling about 2.5 amps and it looks like the ICV was/is pulling around 1 amp when not off. I will stick with the replacement DME (from DUDMD), since the original had some corrosion inside. Maybe my replacement ignition switch is faulty. I can't seem to get the stomp test to work since replacing the switch. I may put the old one back in and see what happens now that there is a different DME in there. I will update accordingly.

[racer2086]

Where'd you get the switch from? New OE?

[goinstrong]

Update: The brake sensor wires have been looped together, and the brake lining warning does not scroll across the dash any more. Also, the ABS light is now out, with that connection having been completed. Also, the battery drain was found and resolved. There was an extra "hot" wire that was connected to the DME harness. It had been spliced in. We risked cutting it, knowing we could always reconnect the wire. As soon as my son cut the wire, the amperage draw went from 2.3 to .6.
We took it for a cruise, and everything works perfectly/properly, so we are actually stumped. I am leaving the battery connected overnight to see what happens. The check engine light went out as well as I was driving, so maybe it is self healing! Haha. I am not sure if I want to mess with success, but I had been planning on putting the old ignition switch back in. I think I will drive it this way for a while and see what transpires...

[Mayorchuck]

I'd be curious to know what aftermarket device was connected to the spliced wire. The brake wear loop has no connection with the ABS at all. Perhaps moving those wires around temp fixed something with the wheel speed sensor wiring or maybe the spliced wire was connected to an ABS related circuit. The check engine light will cycle on and off after a number of engine starts with no error present. If the wire was splice on a BUS wire, it could have cause all sorts of issues.

[goinstrong]

Mayorchuck,

There were actually 4 bare wires in the left rear wheel well. I looped the 2 wires that were for the brake lining sensor together, and connected the "car side" of a wheel sensor to the other 2 bare wires, matching the striped wires together and the solid ones together. The "wheel side" of that speed sensor was still intact, so it fit together nicely. The end result is that I have driven about 100 miles and the ABS light is still gone, and there is no brake pad lining warning scrolling on the dash.
As for the after market wiring in the engine bay eBox, we are completely stumped. There is clearly a hot wire that was spliced into the harness, but it is difficult to trace. All my son and I know is that after cutting it and capping both ends, the drain is gone, and everything still works as is should! I will be replacing the valve cover gaskets and spark plugs tomorrow, and I expect the check engine light to stay out, since the codes could all be caused by very badly leaking valve cover gaskets. I will report back once completed...

[goinstrong]

While a bit of time has passed, I am finally reporting back! Valve cover gaskets, spark plugs, and coil packs replaced. Codes for both 02 sensors (OBD1) came up. I replaced them both, and the car runs perfectly. Thanks for all the help!
Tim