Vanagon TDI ECU problem and replacement ideas

[mStrad]

Hi Everyone

I recently bought an 82 Westy with a 1.9TDI (AHU). The first time I connected my OBD2 reader I was getting an engine coolant temperature sensor fault. It always reads 419F no matter what - cold, hot or not even running. After doing continuity and ohm tests on the ECT sensor and harness, I pin pointed it to the ECU. I sent it in to repair shop and it came back as a processor failure - non repairable.

So I bought another ECU, same bosch/vw part numbers, immobilizer removed but otherwise stock (donor engine came from a 97 Golf AHU). I'm pretty sure my current ECU has been re-mapped/re-tuned to some extent.

The current issues I am experiencing are harder cold starts and the glow plugs always come on for 20sec no matter what the temperature is outside.

My question is would it be best if I try and get my ECU cloned or would a stock ECU still work with minimal changes in HP/torque? I do have VCDS so if anyone knows if I could re-program it myself please post some guidance.

If I am missing any important information please let me know.

[skills@eurocarsplus]

oh boy...

VCDS will let you change *some* parameters but not necessarily let you reprogram your ECU

did the seller give you ANY data on the swap in terms of what may have been done? you could have had a tune for sure...but by who?

the other issue is if you did in fact have a tune on the old ECU some tuners (REVO for example) will lock out the ability to clone the data easily.

seeing you're kind of starting "fresh" with a new ECU i would diagnose any issues you were having as if the system was 100% stock. that will let you weed thru some of the b/s
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[old_man]

I can't help you much with your ECU woes as my AHU doesn't have an ECU. I will tell you, however, that an AHU should have no problems starting in the temperatures you're experiencing right now with out glow plugs.

[valvecovergasket]

[mStrad]

I think re-tuning the replacement is the way to go but I'd really like to find someone who has done it for a Vanagon before. Last thing I'd want is to work with someone who is flying blind

[valvecovergasket]

Like my last post -- Malone tuning
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MegaSquirt resource - SpitfireEFI.com

gone, but not forgotten: '83 tdi westy - swap thread

[mStrad]

Thanks valvecovergasket!

I will contact Malone and see what happens.

[skills@eurocarsplus]

[valvecovergasket]

Checking timing with vcds is worthwhile with this new unit
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MegaSquirt resource - SpitfireEFI.com

gone, but not forgotten: '83 tdi westy - swap thread

[dieseltdi]

Hey first of all the AHU ECU doesn't have an immobiizer so if they told you it had it removed they either don't know what they are talking about or it is a European version. Secondly the ECU is socketed which means you could just swap the chips from your original to the replacement ECU.That way you swap over what every tune was in the original ECU. you might also want to check which temperature sensor they used. IF it is located in a coolant hose rather than on the neck on the side of the block, it probably has an internal coolant leak. These things were notorious for developing leaks that seeped up through the wiring plug and into the harness. I have a AHU in my Vanagon and I used the type with the temp sender on the coolant neck and I have no problems. The Vanagon coolant temp is read from the end of the block using a standard temp sensor probe. Hayden

[mStrad]

Thanks dieseltdi

Yes, it is a European version. The engine/ECU came from Poland. The immobilizer box is actually sitting in the dash. Its been disabled but the OBD2 plug is connected to it for some reason so it has to be there. You are also correct that it can only be tuned with chips since it is too old to be flashed. I found a guy in Germany who sells the chips for the same ECU part number but he says they need to be soldered in. European version different I guess?

As for the coolant sensor, its the 4 pin sensor, part # 6U0 919 501B (yellow band). Its located inside the plastic coolant flange that connects the hose. I checked the resistance across the pins for a variety of different temperatures ( I used an infrared thermometer) and they are all in range according to the temp/resistance curve so based on that I think the sensor is good. The connector plug is pretty dry too.

[mStrad]

Do you guys think there is any danger in plugging in a stock ECU and seeing how it runs?

[dieseltdi]

Try it. It may not run perfectly but it might get get you to a starting point for diagnosis.

[Zeitgeist 13]

[valvecovergasket]

[hans j]

Unplug the cts and see if the temp goes to -40. I suspect you have a wiring issue issue though, but it could be an ecm as well.
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1986 Canadian Syncro Westy TDI - 1989 Syncro Single Cab - 2001 Audi S4 - 1981 VW Caddy ABA - 1980 VW Caddy EV - 1973 VW T-181

[mStrad]

hans j

The temperature on the obd2 reader doesn’t change when I unplug the sensor. It stays at 419f. I’ve confirmed the issue is with the ECU. Sent it to an ECU repair shop, diagnostic test came back as processor failure.

[Zeitgeist 13]

[?Waldo?]

[AndyBees]

OP, I tried to skim thru all the responses, but never saw anything relating to the first issue you were having.... Coolant -419f.

The Coolant Temp Sensor provides data for two places, one for the Temp gauge in the cluster and the other for the ECU. If the CTS goes bad, the Temp reading defaults to something beyond -400F. I've seen several early model (NBs (New Beetles) with a bad CTS and they would emit loads of black smoke! Seems you never mentioned any thing about smoke.

As for the switching of the ECUs, I don't think those early models (AHU) have an immoblizer. So, it should be plug & play. I hope you were able to get your old ECU from the shop. (Well, earlier, I missed the part about the ECU/Engine coming from Poland) ... amazing that the immoblizer function would be handled by a separate module.

As for it not starting well, there are multitude of things that can cause hard starting. Summer months, GPs don't provide much assistance ... temp has to be below 40f, give or take a few degrees, for them to kick-in. So, don't waste your time and money on new GPs.

As others have suggested, you need to scan with VCDS to see what's going on. Once you've scanned, save or write down the codes. Then, clear them and scan again to see what pops. If you get some or all of the same codes, start with the easy one to address and go from there. Also, keep in mind, some codes will not always come back immediately, you probably should do a short test drive, if possible.

Lastly, some of the early (pre-1999.5) ECUs had cold start issues that required a re-flash. And, some had hot hard-starts and some a combo of the two.

Yep, this Thread is not a place to be bashing eTDIs. I love mine and it has proven to be a good choice for over 85k miles ... It has taken on some mighty long road trips and never let me down!
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'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.