VAG Troubleshooting

Diagnosing an Engine Computer can be frustrating. If you're having trouble here are a few things to look for:

1. Check the part number of the unit you have in your vehicle. When looking for the part number, it should be one of the bigger numbers on the label. Now check the invoice of the unit you purchased. Do they match? They need to. If the part number is different, we cannot guarantee the unit will work with your vehicle and could be the reason you're having trouble. 

2. Check the original ECU connector. Are there any burned areas, broken pins or corrosion? There could be a pin stuck in your original connector. This could cause a bent pin which could potentially touch another pin and this can cause some seriously wonky issues all the way up to wiring/ecu damage. The pins can bend even if the connectors are fine. We are very careful with ECU's during programming and shipping but we're not perfect. A pin could have also been bent during installation. A burn mark could also indicate that wire in the connector is burned and completely disconnected further inside. 

3. Have you reconnected all the other connectors and ground straps that may have been disconnected during diagnostics?

4. Have you cleared the check engine lights after installation? This step can sometimes be ignored and the ECU will do it's own self-check but in most cases you SHOULD clear the check engine lights with a scan tool. Residual codes can cause a no start. 

5. Do you have enough voltage in your battery? When a vehicle is down for a while, the battery can start to go flat if it's older. Ensuring your vehicle has a HEALTHY rotation when starting is a must. When the starter is engaged, the battery will pull as many amps as it can to turn the starter, if the battery is low, it might not have enough juice for the coils to properly spark which can cause a no start. 

6. Did you send us ALL of your vehicles information? Was is correct? Can you verify the vin you sent us is correct? If we NEED information, we'll reach out but it's important to know everything was sent correctly.

7. What was the original issue with your car/ECU? Is it exhibiting the same symptoms? If it is, it's possible it's not our unit and perhaps the diagnostic was incorrect. This does not make our ECU bad but rather the vehicle never needed an engine computer installed.

8. Did you fix the original issue in the vehicle before installing a second unit? If the original issue is still unresolved, it's possible the new ECU has suffered the same fate. 

9. Do you have upgrades to your car? This ECU likely wont work for you. We only sell stock replacements. If even something as simple as the MAF was upgraded for an intake, that would throw off the car enough to where it wont start or it'll run very, very poorly.

10. Did your problem start after connecting the jumper cables up backwards(+ to - and - to +?)? If this is the case you VERY LIKELY have an additional module that's dead or severely damaged and before telling us our module is bad the car almost always needs to have a professional look at it. The ECU being dead is only one of MANY other modules on the same circuit. If you swapped battery cables on accident, you need to be aware that many other modules might need replaced. Or even all of them in unlucky scenarios. Do I need to repeat myself again? Reversing polarity in a vehicle is EXTREMELY damaging. Due to this, blaming our unit for the reason the car wont start is completely unreasonable.

Q. My car has new check engine lights on that it didn't have before.

A. It's possible the previous ECU was adapting to the issue at hand over a long period of time. What I mean is if your air filter slowly starts to clog, your car will slowly adapt by adding less and less fuel. It will keep running and still not throw a code but once you erase the adaptation the previous ECU was compensating with or replace the ECU entirely, the new ECU will see there is an error because the new ECU didn't adapt with the vehicle and the issue. This is not always the case and the situation varies but we've seen it before. This can happen with many different types of issues, not just air filters. Oxygen sensors, MAF sensors, pretty much anything that reads on a 5v scale. Which is a lot of them.

Q. How does the immobilizer system work? 

A. Every system is different but commonly, vehicles will have either an external immo box or it will pawn off the task to something like the gauge cluster or body control module. For instance, the MKIV Jetta/Golf. That system stores the immo/key data in the cluster. When the key to the vehicle is inserted into the cylinder, the ring around the cylinder will send a signal to the cluster. That signal is comprised of an RFID number that's unique to that key. The cluster will then cross reference the signal it has against the "database" of keys it has stored on it's internal memory. If the key doesn't match, it will start for 1-2 seconds and then the cluster will send a signal to the ECU to kill the engine. The ECU then set's an immobilizer code: P1570 - Engine Start Blocked By Immobilizer.
This is a general overview of the system but that should give you an idea.

Q. My vehicle starts but I can't read any of the codes. 

A. Depending on the year this could be from another failed module. If it's pre 2005, this is common when things like the radio or the gauge cluster fail. The module that has died will die while communicating on the line and keep every other module from being able to communicate, including the ECU. If this happens, diag can be done by removing fuses to auxiliary modules until you can read codes and you've identified your problem. If it still doesn't allow you to communicate with anything then plug everything back in and try to communicate with every module. The module that DOES communicate is usually the issue. Post 2005, can bus cars, this does not effect the vehicle and can generally be a broken wire to the OBD2 socket or a power/ground issue to the vehicle. 

Q. I installed your ECU and my car starts but it still wont accelerate at all, zero.

A. If you're having issues with your throttle on an Audi/VW car, where the car will start and it idles just fine but the car's throttle pedal will do absolutely nothing? Then you need to look at your Oxygen Sensors. Namely the rear ones. The rear O2's are notorious for being ripped out, especially on lowered cars. When this happens the wires normally touch each other and short out. Because the ECU doesn't have a fuse for the O2 sensors, it fries the smallest trace in the system which is inside the ECU. If you install a new unit without fixing this problem, we can help you but this should be checked BEFORE installing a new unit. See previous Q/A above.

Q. I installed your unit but can't get the keys to adapt with ODIS.

A. There's no need to adapt keys, install the ECU, clear the CEL's, start the car. That's it.

Q. I installed the unit but can not get the keys programmed to my unit!

A. Depending on the situation, you either have an issue with your gauge cluster or external immobilizer box(wherever key data is stored) or more likely, you wont be able to program keys to this unit because you wont need to. 99% Of our units come with the immobilizer removed. This is to alleviate any issues with installation. 

Q: I plugged in the new PCM and have zero communication with the vehicle now.

A: Please check the pins inside the connector. Look for bent or folded pins. We program these on the bench and if we cannot communicate with the unit, we can't program it. If we can't program it, we don't ship it because it would be a very obvious issue. If that looks fine. Plug in the old unit and verify communication. Our unit may have been damaged during shipping.