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How To Outsmart Your Boss On Audi G28
How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49), then to the tachometer in the instrument cluster.


1. Engine Speed Sensor

It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through the grey wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. audi key replacement sends an indication to the G5 Tachometer within 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 trigger spark and injectors in the right way.

If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate an issue with the chain or a jump in the chain link of the upper 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 serve different purposes but the most effective method to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should be reading about 1000 ohms. If you are having problems with this component, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a massive drop in power. It was as if the engine had run out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the fourth one was dry. When I start the engine without sparks, I put a piece of tissue on the top of each of the injector holes and the 3 drenched with gazoline pop out, but the 4th stay shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got 0ohm. I'm assuming that the issue is elsewhere.

I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However the intermittent misfire issue still occurs 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 but the actual pressure is zero.

I'm not sure what to do. I believe that I've ruled everything else out. But i'm worried that I may have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter is similar 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 a parts store. It is simple to test them to do - just put your DMM in resistance mode and take measurements 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

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either of these, the diagnostic scanner will display the codes that could trigger an engine shut down.

Some of the symptoms of a malfunctioning G28 sensor are 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 encounter any of these signs. The good news is that they are very cheap and easily accessible particularly if you're looking at the Bosch unit like ours. Alternately, GM's version this component is a good option.

5. Tachometer

A malfunctioning engine sensor can cause a variety of issues in your car. It's an essential component of the Audi's transmission since it relays information to the ECU about how the car's crankshaft is turning. If the sensor fails, it can disrupt the performance of the transmission as well as the rest of the car's components.

The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The ECU uses this signal to control fuel and boost, and also timig. It also transmits it to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between those two pins. This is the same across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU, so you might find them in wrecking yards.

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