How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is situated near the transmission's edge just above the flywheel gear. It transmits a signal to the ECU via a grey wire (T55/49), then to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via a grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication 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 trigger 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 are not in sync and could indicate the chain is stretched or a jump link on the upper timing chain. However, the code won't appear on its own without additional information from other sensors (G4 and G40).

Testing is a bit tricky since there are two pins for the connector and they serve different purposes however the best method of testing it is to measure the resistance between the sensor and the ECU. When the sensor is functional, it should read approximately 1000 ohms. If you're having issues with this sensor, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed I noticed a massive reduction in power. It was like the engine had run out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs, three were soaked with gazoline and the fourth one was dry. I placed a tissue over each injector hole, and when I start the engine with no sparks, the ones that have gazoline pop right out. The 4th one stays shut. I checked the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. So i assume the problem is in another place.

I also tried to reset the PID without success. The car will start when the G28 is disconnected and it runs perfectly when it is plugged in, but still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. Also i noticed that the gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when I crank up the engine.

I'm not sure what to do, but i feel i have pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. If anyone has suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or parts store. Testing them is easy to do - just put your DMM in resistance mode and measure between pins 1 (with the replacement audi key bump on the connector's end up) and 2 (2nd from the left on the black connector's side). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that has to know the position and speed of the crankshaft to make decisions regarding fuel injector timing etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, the diagnostic scanner will display codes that could lead to the engine shutting down.

A malfunctioning G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, and/or an unfire when in the gear. If you are experiencing any of these issues, it is most likely that your sensor is deteriorating and should be replaced. The good thing is that they are very affordable and easy to find particularly in the case of the check here Bosch model, like ours. Alternatively, the GM version of this part is also a good choice.

5. Tachometer

A malfunctioning engine speed sensor could be the reason behind a slew of issues in your car. It is a website crucial part of your Audi's transmission, since it relays information to the ECU about how the car's crankshaft is turning. When this sensor fails, it will affect the performance of the transmission and the other audi spare key car's components.

The G5 engine speed sensor is situated on the edge of the transmission just above the flywheel ring gear. It sends a signal to the ECU at pin T55/49, via a grey wire. The ECU then uses and processes the signal to control the flow of fuel, timig and boost and then sends here it on to the G5 tachometer inside the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms of resistance between those points. This is a standard component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.