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20 Trailblazers Are Leading The Way In Audi G28
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 situated on the outside of the transmission over the flywheel gear. It transmits a signal the ECU via the 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 above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using a grey wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can start spark and injectors in the right way.

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 possibly indicating chain stretch or a jumped link on the upper timing chain. However, audi a4 spare key won't appear on its own, without additional information from other sensors (G4 and G40).

It can be a bit difficult to test as there are various pins on the connector and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read around 1000 ohms when the sensor is operating at its maximum. If you're experiencing issues with this component, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed, i noticed a huge reduction in power. It was like the engine was running out of gas. Or, my injectors weren't firing. Today, i pulled out the spark plugs, 3 were drenched in gazoline, the fourth was dry. I put a piece of tissue over each hole in the injector and when i turn the engine on without sparks, the three that have gazoline pop right out. The 4th one stays shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero ohm. I think the issue is somewhere else.

I also tried to reset PID without success. The car will start if the G28 is disconnected and it runs perfectly when it is plugged in but it still has intermittent misfire issues at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. I also noticed that the gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, i feel i have pretty much ruled out everything else. I'm worried that i might have missed something. Let me know If you have any suggestions! 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 so you can easily find one at a junkyard or at a parts store. Testing them is easy - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to be aware of the speed and position of the crankshaft to make decisions about timing of the fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go wrong, you will receive codes on the diagnostic scanner that could cause engine shut down.

Some of the symptoms of a malfunctioning G28 sensor include an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or misfiring when you're in gear. It is probable that the sensor is failing and needs to be replaced if you notice any of these symptoms. The good thing is that they are very cheap and readily available particularly when you're looking at an Bosch model, which is what ours are. Alternately, the GM version of this unit is also a good option.

5. Tachometer


A failing engine sensor could cause a myriad of issues within your vehicle. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU about how fast or slowly the car's engine is turning. This sensor can cause the transmission to fail and other car components to be affected.

The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 via an uncolored wire. The ECU utilizes this signal to regulate fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms of resistance between those points. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 Du You may also find some good ones in wrecking yards.

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