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How to Replace an Audi A1 keys G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located at the top of the transmission just above the flywheel ring 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 grey wire is located on the outside of the transmission, above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and the position of the camshaft, to trigger the spark and injectors.

If this sensor fails when it fails, the ECU will display a P00160 error code. 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 jumpy chain link in the upper chain of timing. The code will not appear without the additional information provided by other sensors (G4 or G40).

Testing is a bit challenging because there are two pins for the connector and they serve different purposes however the best method to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is operating at its maximum. Examine for signs of coolant or oil in the connector bay if you have issues with this component.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a massive reduction in power. It was as if the engine had run out of gas. Or, my injectors were not firing. This morning i pull out the spark plugs. Three were drenched in gazoline, the fourth one was dry. When I start the engine without sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline leap out, however the 4th stays shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got 0ohm. I'm assuming that the issue is somewhere else.

I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However, the intermittent misfire problem persists at higher RPM. The coolant sensor (G62) even when unplugged, still shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.

I don't know what to do. I think I've all other possibilities out. I'm afraid i may have missed something. Please let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style sensor is identical to the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or at a parts store. Testing them is easy - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that has to be aware of the speed and position of the crankshaft in order to make a decision about timing of the fuel injector, for example. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have 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 cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, and/or a misfire in the gear. If you experience any of these issues it is likely that your sensor is failing and needs replacing. They are cheap and easy-to-find, especially if they're a Bosch unit like ours. Alternately, the GM version of this unit is also a great option.

5. Tachometer

A failing engine speed sensor could be a cause for a slew of problems in your vehicle. It is a crucial part of your audi q5 key's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. If the sensor fails, it will cause problems for the transmission and the other car's components.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. The ECU then uses and processes the signal to control fuel, timig, and boost, and replacement Audi key Cost also transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. Also, you can 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 see an average resistance of 1000 ohms between these points. This is a typical component across the Replacement Key Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.