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. The sensor is located on the edge 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

It is located on the outside of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using the grey wire. The ECU uses this information to regulate boost and fuel. It also sends signals to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors accordingly.

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

Testing can be a bit difficult since there are two connector pins, and they have different functions but the best method of testing it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms when it is at full operation. If you're experiencing issues with this sensor, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll i had massive power loss like the engine is running out of gas or injectors are not firing any more. I pulled out the spark plugs this morning, three were drenched in gasoline and the 4th was dry. When I crank the engine with no sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline jump out but the 4th stays closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got zero ohm. I think the issue is elsewhere.

I also tried to reset PID but without success. The car will start when the G28 is disconnected and runs fine when it is plugged in however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is zero.

I'm not certain what to do, but i believe that i've completely ruled out all other possibilities. But i am afraid I might have missed something. If anyone has any suggestions, please chime in! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal by the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or parts store. It is simple to test them - simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines must know the speed and position of the crankshaft in order to make a decision about timing of fuel injectors, etc. It uses 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 which can lead to engine shutdown.

The signs of a failed G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when in gear. It is probable that your sensor is failing and needs to be replaced if you notice any of these signs. They are cheap and easy-to-find especially in the case of a Bosch unit like ours. Alternately, the GM version of this unit is also a great option.

5. Tachometer

A faulty engine speed sensor could be a cause for a slew of issues in your vehicle. It is an important part of the transmission in your audi replacement key, as it transmits information to the ECU regarding how fast or slow the engine is turning. This sensor could cause the transmission to fail and other components in the car to be affected.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It sends a signal via a gray wire to the ECU pin T55/49. The ECU then 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 determine if the sensor is in failure by checking continuity from 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 [79trace [79]), and between pin T6a/1 as well as pin T26a/12. It should show approximately 1000 ohms of resistance between these two points. This is a common feature across the replacement audi key fob audi q5 key a4 key [my company] 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU, so you might find good ones in wrecking yards.