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. The sensor is located near the edges of the transmission, above the flywheel ring gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via the grey wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft reached TDC, and where the camshaft lies in order to activate the spark and injectors.

If this sensor fails the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, possibly indicating the chain is stretched or a jump link on the upper chain of timing. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging since there are two connector pins, and they perform different functions but the most effective method of testing it is to measure the resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is operating at its maximum. If you're experiencing issues with this sensor, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the fourth was dry. When i crank the engine without sparks, i place a tissue on the top of each hole in the injector and the 3 drenched with gazoline pop out, but the 4th stay shut. I tested the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I think the issue is somewhere else.

I also tried to reset the PID with no success. The car is able to start if the G28 is unplugged and it runs perfectly when it is plugged in but it still has intermittent misfire issues at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c even when i unplug it. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.



I'm not sure what to do. I feel like i've pretty much ruled everything else out. But i am afraid I may have missed something. If anyone has suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter is identical 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. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black end of the connector). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines must be aware of the position and speed of the crankshaft to make decisions regarding timing of fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If https://notes.io/w2LZ2 are experiencing issues with either of these, the diagnostic scanner will display codes that could cause an engine shutdown.

A malfunctioning G28 sensor can cause an inaccurate speed counter for the gearbox or a gearbox that shifts more quickly than normal, and/or an unfire when in gear. If you have any of these issues it is likely your sensor is failing and requires replacement. https://writeablog.net/grousebronze55/15-terms-everybody-working-in-the-audi-spare-key-industry-should-know are cheap and easy-to-find particularly if they're an Bosch unit like ours. Alternatively, GM's version of this part is an excellent choice.

5. Tachometer

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

The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU then uses and processes the signal to control the flow of fuel, timig and boost, and also sends it on to the G5 tachometer inside the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. You can also check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should observe approximately 1000 ohms resistance between those points. This is a common feature across the Audi 80-100-200-RS2 model, ranging from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 DU, so you might find them in wrecking yards.