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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 sends a message to the ECU via a grey wire T55/49, then to the tachometer on 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 signals to ECU pin T55/49 via an uncolored wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used to connect the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.

If this sensor fails, the ECU will throw 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. The code will not appear without the additional information supplied by other sensors (G4 or G40).

Testing can be a bit difficult since there are two connector pins, and they serve different purposes 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 operating at its maximum. If you are having problems with this component, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, when accelerating from 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 were not firing. I took out the spark plugs this morning, three were soaked with gasoline and the 4th was dry. When I start the engine, there are no sparks, i place a tissue on the top of each hole in the injector and the 3 drenched with gazoline jump out but the 4th one stays closed. I checked the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. So i assume the problem is elsewhere.

I also tried to reset the PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. audi a3 replacement key www.g28carkeys.co.uk noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine.

I don't know what to do. I feel like i've pretty much eliminated everything else. However, i'm afraid that I might have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or a parts store. Test them out to do - just 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

The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either one of these, the diagnostic scanner will display the codes that could trigger the engine shutting down.

A damaged G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, and/or a misfire in gear. It is possible that your sensor is failing and requires to be replaced if you experience any of these signs. The good news is they are very cheap and easily accessible, especially if you're looking at an Bosch sensor, which is what ours are. Alternately, GM's version this part would be an option.

5. Tachometer

A malfunctioning engine speed sensor could be a cause for many problems in your car. It's an essential component of the Audi's transmission as it sends information to the ECU about how the car's crankshaft is rotating. When this sensor fails, it will affect the performance of the transmission, as well as the rest of the car's components.

The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to regulate the amount of fuel and boost, as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by checking 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 [79trace [79]), and between pin T6a/1 and pin T26a/12. You should detect an average resistance of 1000 ohms between these points. This is a typical component across the Audi 80 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.