10 Quick Tips On Audi G28

How to Replace an Audi a5 Key fob G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission over the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU uses this information to control the amount of fuel and boost. It also sends a signal to the G5 tachometer in the instrument cluster.

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

If this sensor fails when it fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumped chain link in the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging because there are two connector pins, and they serve different purposes however the best method to test it is by measuring resistance between the sensor and the ECU. When the sensor is functional, it should read about 1000 ohms. Check 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 full speed I noticed a significant drop in power. It was as if the engine was running out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning, 3 were drenched in gasoline and the fourth was dry. I put tissue over each hole in the injector and when i turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one remains closed. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I got 0ohm. So i assume the problem is elsewhere.

I also tried to reset PID but without success. The car is able to start if the G28 is disconnected and runs fine when it is plugged in but it still is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when unplugged, still shows an ice temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit is showing 2 bar when the actual pressure is 0.0 if i crank up the engine.

I'm not sure what to do, i think i've pretty much eliminated everything else. I'm worried that i might have missed something. Let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. It is simple to test them - just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that has to know the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, for example. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

Some of the signs of a failing G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when you are in gear. It is probable that the sensor is failing and needs to be replaced if you experience any of these signs. The good news is that they are very cheap and easy to find, especially if you're looking at an Bosch model, which is what we have. If you prefer, GM's version of this part would be a good option.

5. Tachometer

A failing engine speed sensor could be a cause for a slew of issues in your car. It is an important part of the transmission in your audi tt key because it relays information to the ECU on how fast or slowly the engine is turning. If this sensor fails, it will cause problems for the transmission and the other car's components.

The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits an electrical signal through a gray wire to the ECU pin T55/49. The ECU is then able to process the signal to control fuel, timig, and boost as well as sends it on to the G5 tachometer in the instrument cluster. You can check for sensor Audi A1 key replacement failure by examining the continuity of the sensor to the tachometer. Also, you can examine the continuity between pins 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 part across the audi remote key 80, 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.