How to Replace an audi a3 key G28 Engine Speed Sensor

In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is situated near the edges of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via a grey wire (T55/49) and then to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, directly above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used to link the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors in the right way.

If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).

Testing can be a bit difficult because there are two connector pins, and cheapest they serve different purposes but the most effective way to test it is to measure resistance between the sensor and the ECU. When the sensor is operational, it should read around 1000 ohms. Look for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced an abrupt drop in power like the engine is out of gas or injectors are not firing at all. I took out the spark plugs this morning, 3 were drenched in gasoline and the 4th was dry. When I crank the engine with no sparks, i place a tissue on the top of each hole in the injector and the 3 that were drenched in gazoline jump out but the 4th stay shut. I tested the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming the issue is in another place.

I also tried to reset the PID but with no luck. The car will start if the G28 is disconnected and it runs perfectly when it is connected however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when unplugged, still shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is 0.

I don't know what to do. I think I've all other possibilities out. But i am afraid I may have missed something. Let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sensor is identical to the G4 and they both work in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or at a parts store. It is easy to test them - simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines needs to know the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either one of these, the diagnostic scanner will display the codes that could trigger an engine shut down.

Some of the symptoms of a malfunctioning G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal, audikey and/or a misfire when you're in gear. It is likely that your sensor is failing and requires to be replaced if you encounter any of these signs. They're inexpensive and easy to locate particularly when they're a Bosch sensor like ours. Alternately, GM's version this part would be a good option.

5. Tachometer

A damaged engine sensor could cause a myriad of issues within your vehicle. It's an essential component of the transmission of your audi tt key case since it sends information to the ECU about how fast or slow the audi car key case's engine is spinning. This sensor can cause the transmission to malfunction and other car components to be affected.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. The ECU then uses and processes the signal to control fuel, timig and boost and then transmitting it 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. You can also check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. You should detect the resistance to be around 1000 ohms between these two points. This is a common component across the audi a5 key fob 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.