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How to Replace an audi key fob not working G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located on the outside of the transmission over the flywheel gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using an uncolored wire. The ECU utilizes this information to control boost and fuel. It also sends a signal to the G5 Tachometer located in 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 reached TDC, and where the camshaft lies so that it can activate the spark and injectors.

If this sensor fails to function, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jump in the chain link of the upper chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).

Testing can be a bit difficult because there are two connector pins and they have different functions however the best method of testing it is to measure resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading around 1000 ohms. Check for signs of coolant or oil in the connector bay if you are experiencing problems with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant decrease 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 drenched in gazoline, the 4th one was dry. When I start the engine with no sparks, i place a tissue on the top of each of the injector holes and the 3 drenched with gazoline pop out, audi a4 Replacement key but the 4th stay closed. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get zero Ohm. I'm assuming that the issue is in another location.

I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it runs fine with the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.

I'm not certain what to do, but i think i've pretty much eliminated everything else. However, i'm afraid that I may have missed something. If anyone has any suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and both are used in the 80 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or at a parts store. It is easy to test them - just put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines needs to know both the speed and position of the crankshaft to determine timing of the fuel injector, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go bad you will get codes on the diagnostic scanner which can cause the engine to shut down.

Some of the signs of a failed G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when you are in gear. If you experience any of these issues, it is most likely that your sensor is deteriorating and requires replacement. They are cheap and easy-to-find, especially in the case of an Bosch unit like ours. If you prefer, GM's version of this component is an option.

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 Q3 key because it relays information to the ECU about how fast or slow the car's engine is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.

The G5 engine speed sensor is located at the outside of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU is then able to process the signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. You can also 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 see an average resistance of 1000 ohms between these two points. This is a standard part that is found across the audi keyless entry 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.