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How to Replace an replacement Audi a3 key G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49) which is then sent to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated at the edges of the transmission, directly above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

It is a little tricky to test because there are various pins on the connector and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. If the sensor is functional, it should read around 1000 ohms. If you're experiencing issues with this sensor, look for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge reduction in power. It was as if the engine was running out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning, three were soaked with gasoline and the fourth was unclean. When I crank the engine with no sparks i put tissue on the top of each of the injector holes and the 3 drenched with gazoline pop out, but the 4th stays closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I got zero Ohm. I assume that the problem is in another location.

I also tried to reset PID without success. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.

I don't know what to do. I believe that I've eliminated everything else. But i am afraid I may have missed something. If anyone has any ideas please let me know! TIA!

3. Fuel Pump

The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or Replacement Audi A3 Key parts store. Test them out by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black end of the connector). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft in order to make decisions regarding fuel injector timing etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

Some of the signs of a failing G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when you are in gear. If you have any of these issues it is most likely that your sensor is going bad and needs replacing. They're inexpensive and easy to locate particularly if they're a Bosch model like ours. Alternately, GM's version this part is an option.

5. Tachometer

A failing engine speed sensor could be the reason behind a slew of issues with your vehicle. It's a vital component of the audi smart key replacement's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is spinning. If this sensor fails, it could disrupt the performance of the transmission, as well as the other car's components.

The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via a grey wire. The ECU then uses and processes this signal to control fuel, timig, and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should see the resistance to be around 1000 ohms between these points. This is a typical component across the audi a3 replacement key 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.