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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. The sensor is located near the transmission's edge, above the flywheel gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer on 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 a signal via the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends signals to the G5 tachometer in the instrument cluster.

The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft reached TDC, and the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails, the ECU will display a P00160 error message. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumped chain link in the upper timing chain. The code won't appear without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging since there are two pins for the connector and they serve different purposes but the best method of testing it is by measuring resistance between the sensor and the ECU. If the sensor is functional, it should read approximately 1000 ohms. Look for evidence of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll, I experienced massive power loss as if the engine was running out of gas or the injectors aren't firing anymore. Today, i pulled out the spark plugs, three were soaked with gazoline and the fourth one was dry. When I start the engine without sparks, i place a tissue on the top of each hole in the injector, the 3 drenched with gazoline jump out but the 4th stay shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I got 0ohm. I'm assuming the issue is elsewhere.

I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.

I don't know what to do. I think I've all other possibilities out. I'm concerned that i may have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump in 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 an extra in a wrecking shop or In My Area a parts store. Testing them is easy to do - just put 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 left on the black end of the connector). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that must know the position and speed of the crankshaft to make decisions regarding fuel injector timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go bad you will get codes on the diagnostic scanner that can cause the engine to shut down.

A malfunctioning G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, or a misfire while in the gear. If you have any of these issues, it is most likely that your sensor is deteriorating and requires replacement. They're cheap and easy to find, especially if they're a Bosch sensor like ours. Alternately, GM's version this part would be an option.

5. Tachometer

A failing engine sensor could cause a myriad of issues in your car. It is a crucial part of the audi a4 key replacement's transmission since it relays information to the ECU about how fast or slow the car's crankshaft is turning. When this sensor fails, it will cause problems for the transmission, as well as the other car's components.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits an electrical signal through a gray wire to the ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is In My Area 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 approximately 1000 ohms of resistance between these two points. This is the same across the audi tt key programming 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 Du So, you may find them in wrecking yards.