Help Diagnosing TPS Code 1216 on a Dinan Supercharged 95 M3

[Braymond141]

I need some help on this one. OBD1 is the worst and this code has been driving me (and the owner) nuts for the past 6 months.

First off; Yes, we have searched and searched and searched. Yes, we have thrown all sorts of parts at this. Please do not rehash known threads or fixes that have already been mentioned. I guarantee, short of an oscilloscope, we have tried it.

10/1994 build date 95 M3 with 89k miles
506 EWS ECU with a legit Dinan chip ordered specifically for this car and with their spec'd 2.7k ohm MAF signal wire resistor.

This car ran perfect NA, flew out to Colorado to install this kit for a friend and have been plagued by this code since. The car runs and drives absolutely perfect until it idles at operating temperature for more than a minute and then the check engine light pops for TPS (1216) and throttle goes to shit. Shut off and restart, the problem goes away until it is idling for more than a minute and 1216 again. Over and over. You can drive for as long as you want and the code never pops until you let it idle longer than a minute. There are no other codes. If the code is not present, it idles perfect and throttles all the way to redline without issue.

What we have done;
-Tried MULTIPLE OBD1 SC tunes. Dinan for Powerdyne, Dinan for Vortech, RK, and also different ECUs with the matching tune for that ECU.
-Three different ECUs. All throw the same code. Two ECU are 413 and one is a 506. The 506 is original to his car.
-Inspected all wiring from connector to DME. All perfect. His car is unmolested, super super clean and everything associated to wiring is untouched. There are no melted wires or shorts found.
-Replaced the TPS sensor with four others that are known good. All sensors read perfectly in off position 1.3kohm-4.3kohm, 5v rail GOOD, and both ascending and descending voltages are spot on with zero issues on the full sweep. Pin 1 and 3 3700ohm sweep test also passed too (stays 3700ohm for the entire throttle sweep)
-Replaced the throttle with two used units and one brand new freshly ordered Dinan TB. The idle set screw is 100% not the problem.
-Throttle cable is not cracking the plate open at all. Cable tension is not the issue.
-Tried three different Genuine BMW MAF. Not the issue.
-Tried some random BFc post stating Dinan is giving out the wrong 2.7k ohm spec and the real spec is 3.6k ohm resistor. Not the issue.
-New OE front and rear knock sensors
-New OE Crankshaft sensor
-New OE Camshaft sensor
-New OE Main Power Relay
-Alternator voltage regulator tear down, cleanup and inspection. Not the issue and voltage is perfect.
-AC on for increased idle speed. Didn't work. Have not tried a higher custom idle, but we should not have to be forced into resorting to this.
-Replaced the blue ECU read head coolant temp sensor. No change. Unplugged the cluster temp sensor. No change. The TPS shares ground with the head temp sensors per a post on here.
-ICV is perfect and was cleaned while the manifold was off.
-RallyRoad ICV adapter and boost proof hoses are being used. There are NO leaks.
-Manifold has new gaskets, Injectors have new orings.
-Every part of the Dinan kit is to spec. I've done almost a dozen OBD2 installs with ZERO issues. Only this trash OBD1 system is kicking my ass.
-One BFC post said he fixed the problem by heat shield wrapping the TPS sensor wire because "it would get hot and change resistance". Tried this, no change.
-Capped off the throttle body port for fuel ventilation system. No change.
-Sent him an INPA ADS setup for diagnoses. You can't live view certain data with OBD1 while running (did not know that), but with engine off, everything is perfect including throttle % and voltage.
-Passenger side ground strap is in perfect condition and this car has been CO owned from new with zero corrosion of any sort.
-Tried clocking the MAF towards the fender. No change.

There are numerous 1216 TPS code posts across multiple forums. We've tried everything mentioned. Our only option at this point is to blame the tune (we've tried so many), or replace the entire engine harness. Any help is appreciated.

[Greenday694]

I know what you mean. I've had my share of electrical problems with my E36 as well. Unfortunately no matter how well maintained or how low the mileage is, the wire harness and electrical connectors do fail overtime.
What I suggest is use 2 voltmeter,
Use the one to back probe the ECU connector, between sensor ground and 5 volt reference. Use the other voltmeter to back probe, the TPS signal to ground.
Start the engine let it idle for the one-minute time and see if there is any anomalies.
If everything Hold Steady, up to the check engine light coming on again, I would definitely say something is not right with the tune.

Sent from my VS995 using Tapatalk

[Hova]

Any updates on this?

[Braymond141]

Any updates on this?

Replaced the MAF again, no change. He's ordered some more parts to try and I mailed him some modified versions of the Dinan chip to see if one of them corrects the issue. One is just an 850rpm idle (instead of 650) and the other is higher idle and no o2 sensor input.

[AJLM34A]

Which wire(s) for the TPS did you shield? Fab up a 3 wire TPS harness with a replacement ODB-1 TPS connector that can bypass the 26 year old factory engine harness. Supply him with a tool to push the terminals out of the DME connector and 3 new terminals, or he can tie in the ground at the splice for pin 71 since there are no codes for anything else that shares that ground.

Easier and cheaper than replacing the engine harness.
Screen Shot 2020-03-30 at 10.44.37 AM.png

[Braymond141]

More updates;

-New Genuine 502 MAF; no change
-New head temp sensors; no change
-New TPS; no change
-New O2 Sensor; no change
-Sent him a smoke tester. Found that the oring on the RR ICV adapter was rolled over and crushed. Fixed, zero leaks; no change

OBD1 is the worst.

[jmargo]

Have you tried with the SC belt removed ?
How about once its at temp and acting up plug in the old ecu water temp sensor and see if it idles better. Just hold it and possibly ground it to something. That may narrow down a harness issue.

[Braymond141]

Have you tried with the SC belt removed ?
How about once its at temp and acting up plug in the old ecu water temp sensor and see if it idles better. Just hold it and possibly ground it to something. That may narrow down a harness issue.

Unplugged the ICV and everything is perfect. Sent him a new ICV, same 1216 problem.

He’s just going to run with the ICV unplugged until I can come out again and tackle some new ideas.

My latest thought is maybe replacing the OE ICV fitting with the RallyRoad part is causing the issue. The OE part has half the orifice take up by the vacuum fitting that leads to the valve cover breather. Maybe the tuning is just ultra sensitive to that being gone.

[SlumdogJay]

For what it’s worth I have the factory ICV fitting in and my car is doing the exact same thing as this car. I only recently came across this thread and found that pulling ICV did the same thing for me. Once pulled everything was perfect but leave it plugged in and after a minute check engine light is back code 1216. 413 red label with Miller war chip in my case but from what I can gather the exact issue you are experiencing. Let me know if I can help I want to help future obd1 tubo folks who may have this issue

[Braymond141]

For what it’s worth I have the factory ICV fitting in and my car is doing the exact same thing as this car.

Well, fuck.

I swear, every road leads to this being a tuning issue.

[SlumdogJay]

I have a KDATA ecu also and it will start the car but it won’t run but I’m gonna run back through the settings to make sure everything is correct. I saw somewhere there may be a way to sorta hijack the information from the factory DME while its running and put it into datalogger I may investigate this a little further.

[M3poseur]

Braymond141, any update on the issue?

[BMWManiac]

I'm subscribing for the simple fact that I had the SAME error with the TPS CEL when I ran TRM's OBD1 turbo tune....they didn't identify the culprit unfortunately and I've moved onto a different setup/tune. Mine would always occur though while driving around 65 mph at a constant rate.

Maybe the solution is just convert to OBD2! Yes, more money, but if it solves it, it is worth the peace of mind. I get it though...it is now the principal of the matter and you want to figure it out.

[Braymond141]

Braymond141, any update on the issue?

Nope. Still an issue and is being bypassed by driving with the ICV unpluged. OBD1 is the fucking worst.

I'm subscribing for the simple fact that I had the SAME error with the TPS CEL when I ran TRM's OBD1 turbo tune....they didn't identify the culprit unfortunately and I've moved onto a different setup/tune. Mine would always occur though while driving around 65 mph at a constant rate.

Maybe the solution is just convert to OBD2! Yes, more money, but if it solves it, it is worth the peace of mind. I get it though...it is now the principal of the matter and you want to figure it out.

I wouldn't mind converting him but his car is also low mileage and a very rare spec.

[BMWManiac]

Is there an adjustment screw like the e30 on the obd1 throttle body?

Any chance he would be willing to go back to stock to see if the problem persists?

[Braymond141]

Is there an adjustment screw like the e30 on the obd1 throttle body?

Any chance he would be willing to go back to stock to see if the problem persists?

Yes, but for starters it was never touched on any of the three stock throttle bodies that were tried and the NEW Dinan throttle body that is now installed is preset by Dinan. Why would anyone need to touch this? You also cannot adjust it with the throttle installed, it must be removed.

No.

[5mall5nail5]

Yes, but for starters it was never touched on any of the three stock throttle bodies that were tried and the NEW Dinan throttle body that is now installed is preset by Dinan. Why would anyone need to touch this? You also cannot adjust it with the throttle installed, it must be removed.

No.

Not true - I adjust my throttle body gap without removing the TB. When I was poor and in college this WAS my ICV

That said - you said short of an oscilloscope. Why? Put one on it. Cheap AF USB scopes out there, see what the TPS sensor is doing. I have seen ALL SORTS of EMI/RFI noise on these cars. The coil pack system is SUPER noisy into the ground plane. I am probably the only one grounding the coils to the extent that I am.

[Braymond141]

Not true - I adjust my throttle body gap without removing the TB. When I was poor and in college this WAS my ICV

Mostly true. Releasing the jam nut does not exactly free up the set screw for easy turning. You cannot access the the proper way to turn it in and out without removing the throttle body.

[M3poseur]

Obd1 is just plain horrible. Not knowing what the dme is seeing is not helping with troubleshooting.

I am in a process of replacing my whole harness chasing my running rich issue. Just like you, I have replaced every parts and exhausted my option. We redo the hot and cold side piping. Now the car is running pig rich!

If engine harness swap doesn’t fix this. I am swapping to Obd2.

[5mall5nail5]

Mostly true. Releasing the jam nut does not exactly free up the set screw for easy turning. You cannot access the the proper way to turn it in and out without removing the throttle body.

Pay me my hourly rate and i'll go rotate it on video for you

[Braymond141]

Pay me my hourly rate and i'll go rotate it on video for you

No thanks. The throttle body is not the issue.

[5mall5nail5]

No thanks. The throttle body is not the issue.

According to the code, something about the TPS is.

Sounds like you're running a shop - this is a worthwhile tool to have: https://www.amazon.com/Rigol-DS1102E...6066956&sr=8-7