# 1995 Jetta III GLS 2.0l: - No check-engine light?



## Kirbentech (Dec 17, 2008)

*1995 Jetta III GLS 2.0l: - No check-engine light = faulty ECM?*

I have been trying to diagnose why this car will not start. 

After using the paper clip method to check engine codes I realized that the check-engine light does not light up - even with just turning on the ignition. 

I verified that the check-engine bulb works. All fuses are good. 

Does this simply point to an ECM issue, or am I missing something obvious to check? 

More of the story: I replaced the timing belt many months ago. After installing the belt (before I put everything else back together) I started the car for a few seconds - just to make sure it would start. 

Many months later when I decided to finish the job, the battery was dead. I charged up the still-installed battery. The car would not start at this point. The only other thing I did to the car was to take out the aftermarket stereo (in preparation for selling the car). 

Could I have have messed up the ECM by trying to jump-start (and later charge) the battery (thinking voltage surge here...)? 

Thanks for your help... 

Kirby - in Colorado


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## blacksanta (Aug 8, 2009)

Could be a relay going(gone). I think it's #12(double check though) above the fuse box. Or it could be the factory alarm not letting the car start. What radio were you going to put in? An oem one? Do you have the code for the oem radio?


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## skip57 (Nov 7, 2008)

First things first make sure the radio and alarm system are not the problem (look in the stickies for the right way to disable both) 

Check the ignition switch 
check for power at the ECM relay 
Is power getting to the ECM 
Is the fuel pump coming on when you turn the key on? 
If you don't have the CEL lite on (the ECM is not getting power) 
GROUNDS ALL 

A little out of order but a place to start


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## Kirbentech (Dec 17, 2008)

Update: 

Blacksanta - the radio I removed was an older aftermarket CD stereo. I moved it to another vehicle in preparation for selling the Jetta (minus the radio). 

Verified power to the #12 relay. I could hear and feel the relay activating. 

I then decided to pull all the radio-related wires out of the stereo opening to see if anything looked cut that should not have been cut. I nicely shorted out something, and successfully succeeded in eliminating any signs of life in the car (turning on the ignition no longer does anything - no more idiot lights, no more power to #12 relay). 

I looked at most of the related fuses in the panel, but all were okay. I'll look at the wiring diagrams in the book to see where any other upstream fuses are. 

Skip 57 - As soon as I get the current issue figured out, I'll check out power to the ECM... 

Stay tuned... 

Kirby


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## blacksanta (Aug 8, 2009)

good Luck. Keep us posted.:beer:


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## owmygulay (Nov 22, 2009)

I think the ecm relay is #3. Second row up and third from the left. It is labeled 109. I just had the same problem. The give away is not getting the check engine light when you turn the key on. It is now the ignition switch or anything like that.


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## ps2375 (Aug 13, 2003)

Have you checked the actual bulb for the CEL? It is a bulb, not an LED, it could be bad or missing.


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## Kirbentech (Dec 17, 2008)

*1995 Jetta III GLS 2.0l: - No check-engine light = faulty ECM?*

I realized at some later point that I had only checked the fuel pump relay, and still had to verify the ECM relay. 

That's about the time I shorted out the always-on radio power wire (which took out all power to anything in the car). Next week I need to figure out where there is a fusible link. Back to the Bentley!


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## Kirbentech (Dec 17, 2008)

*1995 Jetta III GLS 2.0l: - No check-engine light = faulty ECU?*

Finally made it back out to work on the car... 

The good news is that whatever shorted out must not have shorted out - because a week later or so later (yesterday), I once again had power inside the car. 

I verified power to the other appropriate relays. 

I have unbolted the ECU and am now at the point of taking off the connector. What part of the connector comes off? It looks like if I pry something, the plastic will break. I see four hex (?) screws on the metal cover-part, but I doubt that is it. 

Questions: 
1. How does the ECU connector come off? 
2. What electrical thing stopped working when I shorted the radio power wire, but came back on sometime during a week of letting it just sit? 

Thanks! Kirby


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## skip57 (Nov 7, 2008)

The ECM wiring harness has a slide lock to keep it in place with the ECM. 

VW does use a thermo fuse (circuit breaker) 



just reread the post 

Check all the grounds 

OHM out the must have sensors and the coil 

at this point does it crank over but not start is the CEL on W/key on 

Have you checked the speed/crank sensor 

Again a little out of order just typing then thinking


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## Kirbentech (Dec 17, 2008)

*1995 Jetta III GLS 2.0l: - No check-engine light = faulty ECU?*

Skip57 - thanks for your continued suggestions. 

I'll take my next look at the car on Tuesday. 

There is no CEL at any position of the key. I've verified the bulb. Cranks nicely. No spark. 

I'll see what slides on the ECM. Sounds much better than simply prying it off! 

I'll check the other items you suggested on Tuesday. 

Thanks again! Kirby


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## Kirbentech (Dec 17, 2008)

*1995 Jetta III GLS 2.0L: - No check-engine (MIL) light?*

Here's an update...

I replaced the ECM / ECU with a used unit (same numbers on the replacement ECM / ECU). Seeing the MIL light up was encouraging, and the car immediately started up.

After around 10 seconds the MIL / CEL came on. I tried checking for the blinking MIL codes, but it never blinks. Jumpering 4 & 15 makes the light go out, but the light never blinks. Would a V.A.G.-type of tool tell me what the problem is?

The car runs fairly well (especially for not having been driven in at least 18 months), but appears to lack power (old gas, probably a little gummed up, etc.).

Any ideas on the MIL / CEL? 

Thanks - Kirby


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## Elessar_lad (May 12, 2012)

Kirbentech said:


> Here's an update...
> 
> I replaced the ECM / ECU with a used unit (same numbers on the replacement ECM / ECU). Seeing the MIL light up was encouraging, and the car immediately started up.
> 
> ...


Hi

I have a very similar issue with the MIL on my car, checked the bulbs, fuses, relays, just like you no MIL, no light with the paper clip thing I had the ECU burnt and I'll have it fixed/replaced soon will let you know about the MIL/Check engine


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