How to Replace an audi a1 key replacement G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located on the outside of the transmission, above the flywheel gear. It transmits a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer within the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends signals to ECU pin T55/49 via the grey wire. The ECU uses this information to control fuel and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.

The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors in the right way.

If this sensor fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate a chain stretch or a jumpy chain link in the upper timing chain. The code will not appear 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 but the best method to test it is by measuring resistance between the sensor and the ECU. If the sensor is operational, it should read approximately 1000 ohms. If you're having issues with this component, look key for audi evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had massive power loss like the engine is out of gas or the injectors aren't firing anymore. Today, i pulled out the spark plugs. Three were soaked with gazoline and the fourth one was dry. When I crank the engine without sparks i put tissue on the top of each hole in the injector, the 3 drenched with gazoline jump out but the 4th one stays closed. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I think the issue is somewhere else.

I also tried to reset the PID but without success. The car can start when the G28 is not plugged in and is running fine when it is plugged in, but still has the intermittent misfire issue at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.

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

3. Fuel Pump

The fuel pump in the g28 receives 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 which is why you can easily locate one at a salvage yard or at a parts store. Test them out - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's end). They should be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that needs to know the speed and position of the crankshaft in order to make decisions regarding fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you encounter a problem with either one of these, the diagnostic scanner will display codes that could lead to an engine shut down.

A failing G28 sensor could cause an inaccurate speed counter for the gearbox and a gearbox which shifts more quickly than normal, and/or a misfire while in gear. It is probable that your sensor is failing and needs to be replaced if you notice any of these symptoms. They are cheap and easy-to-find, especially when they're an Bosch unit like ours. Alternatively, the GM version of this component is also a great option.

5. Tachometer

A malfunctioning engine speed sensor could be the reason behind a slew of issues with your car. It's an essential component of the transmission in your audi key copy because it relays information to the ECU about how fast or slow the engine of the car is turning. When this sensor fails, it will disrupt the performance of the transmission, as well as the other car key Replacement Audi's components.

The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It transmits a signal via a gray wire to the ECU pin T55/49. The ECU uses this signal to control the amount of fuel and boost, and also timig. It also sends it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in 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 and pin T26a/12. You should observe around 1000 ohms of resistance between those two pins. This is a standard part that is found across the replacement audi key fob 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.