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How to Replace an audi replacement car keys G28 Engine Speed Sensor

Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is situated at the top of the transmission, above the flywheel ring gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer located in 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 a signal to ECU pin T55/49 via a grey wire. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends an indication to the G5 Tachometer in instrument cluster.

The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also where the camshaft lies so that it can activate the spark and injectors.

If this sensor fails the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain stretching or a jump link on the upper timing chain. The code won't appear without the additional information supplied Near by other sensors (G4 or G40).

It is a little tricky to test as there are different connector pins, and they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. If the sensor is functional, it should read about 1000 ohms. If you're experiencing issues with this part, check for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll, I experienced an abrupt drop in power as if the engine was running out of gas or the injectors are not firing any more. I took out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. I put tissue over each hole in the injector and when i start the engine with no sparks, the ones with gazoline jump out. The 4th one remains shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get 0ohm. I'm assuming that the issue is in another location.

I also tried to reset PID without success. The car will start when the G28 is unplugged, and services it runs fine with the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -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 don't know what to do. I feel like i've pretty much all other possibilities out. I'm afraid i may have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal from the RPM sensor. The GM-style sensor is the same as the G4 and they both work in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. Test them out - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's side). They should be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injector, for audi Key fobs example. It utilizes 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 show codes that could lead to an engine shut down.

A malfunctioning G28 sensor could result in an inaccurate speed counter for the gearbox and a gearbox which shifts faster than normal, or a misfire in gear. If you are experiencing any of these issues it is likely that your sensor is deteriorating and should be replaced. They are cheap and easy-to-find, especially if they're an Bosch sensor like ours. Alternatively, the GM version of this part is also a great option.

5. Tachometer

A failing engine speed sensor could be a cause for a slew of problems in your car. It's an essential component of the transmission of your key audi because it relays information to the ECU regarding how fast or slow the engine of the car is spinning. This sensor could cause the transmission to fail and other components in the car to be affected.

The G5 engine speed sensor is located on the outside of the transmission just above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via an uncolored wire. The ECU is then able to process this signal to regulate fuel, timig, and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between those points. This is a standard component across the audi a3 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.