4 Dirty Little Tips About Audi G28 Industry Audi G28 Industry How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the outside of the transmission, above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors according to the situation.

If this sensor fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumped chain link in the upper timing chain. 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 pins for the connector and they perform different functions but the most effective method of testing it is by measuring resistance between the sensor and the ECU. If audi keyfob is operational, it should be reading around 1000 ohms. If you're having issues with this sensor, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, I experienced an abrupt drop in power like the engine is out of gas or injectors are not firing any more. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was unclean. I put tissue over each injector hole and when i start the engine without sparks, the ones with gazoline jump right out. The fourth one remains shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found 0ohm. I think the issue is in another location.

I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.

I'm not certain what to do, i feel i have pretty much ruled out everything else. However, i'm afraid that i might have missed something. If anyone has suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style sender 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 wrecking yard or at a parts store. Testing them is easy by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to know the position and speed of the crankshaft to determine timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go bad you will get codes on the diagnostic scanner which can lead to engine shutdown.

A malfunctioning G28 sensor could result in an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire in the gear. If you experience any of these issues it is likely your sensor is deteriorating and should be replaced. The good news is that they are very cheap and easily accessible particularly if you're looking at an Bosch sensor, which is what ours are. Alternately, the GM version of this component is also a good option.

5. Tachometer

A failing engine sensor could cause a variety of issues in your vehicle. It's a crucial component of the transmission of your Audi because it relays information to the ECU regarding how fast or slow the car's engine is turning. If the sensor fails, it could affect the performance of the transmission, as well as the rest of the car's components.

The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear. It sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then processes this signal to regulate the flow of fuel, timig and boost, and also sends it on to the G5 tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 as well as pin T26a/12. You should detect an average resistance of 1000 ohms in these areas. This is a typical component across the Audi 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.