How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, directly above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate boost and fuel. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors according to the situation.

If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate an issue with the chain or a jump in the chain link of the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).

It can be a bit difficult to test as there are several connector programmers pins, and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. It should read approximately 1000 ohms when the sensor is at full operation. Look for signs of coolant, or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday, when accelerating from highway paytoll at a high speed I noticed a significant 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, 3 were soaked with gazoline and the fourth one was dry. I placed a tissue over each hole in the injector and when i start the engine without sparks, the ones that have gazoline pop right out. The fourth one remains closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero Ohm. I assume that the problem is somewhere else.

I also tried to reset PID without success. The car is able to start if the G28 is disconnected and is running fine when it is plugged in however it is experiencing intermittent misfires at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c even when i unplug it. Also, i noticed that the gauge key for audi 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 certain what to do, i feel i have pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. If anyone has any suggestions, please chime in! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter is identical to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or a parts store. It is easy to test them - just switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines must know the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these, the diagnostic scanner will display codes that could lead to an engine shutdown.

The signs of a failed G28 sensor include an inaccurate rev counter for the gearbox and gears that shift faster than normal, and/or a misfire when in gear. It is possible that your sensor is failing and requires to be replaced if you encounter any of these signs. The good news is that they are quite affordable and easy to find particularly in the case of an Bosch sensor, which is what we have. Alternately, the GM version of this component is also a good choice.

5. Tachometer

A faulty engine speed sensor could be the reason behind a slew of problems in your vehicle. It is a crucial part of your audi car keys's transmission, since it relays information to the ECU about how fast or slow the vehicle's crankshaft is spinning. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It transmits an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU uses this signal to regulate the flow of fuel and boost and also timig. It also relays it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Also, 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 as well as pin T26a/12. You should observe approximately 1000 ohms resistance between those two pins. This is a common feature across the audi spare key cost 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du, so you might find some good ones in wrecking yards.