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How to Replace an Audi car key case G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located near the transmission's edge, above the flywheel gear. It transmits a signal the ECU via a grey wire (T55/49) and then to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, directly above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate boost and fuel. It also sends signals to the G5 tachometer inside the instrument cluster.

The sensor is used to connect with the G40 Camshaft position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also the position of the camshaft, to trigger the spark and injectors.

If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

Testing is a bit tricky since there are two connector pins, and they have different functions however the best method to test it is to measure resistance between the sensor and the ECU. When the sensor is fully functional, it should read about 1000 ohms. Look replacement key for audi a3 evidence of coolant or oil in the connector bay if you have issues with this part.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive decrease in power. It was as if the engine was running out of gas. Or, my injectors weren't firing. Today, i pulled out the spark plugs, three were soaked with gazoline and the fourth one was dry. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the three with gazoline jump out. The fourth one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. So i assume the problem is in another place.

I also tried to reset the PID without success. The car will start when the G28 is disconnected, Audi A3 Spare Key but it runs fine with the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows an ice temperature of -49c. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 when i rev the engine.

I'm not sure what to do, as i feel i have pretty much ruled out everything else. I'm worried that i might have missed something. Please let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style sensor is identical to 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. It is easy to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines needs to know the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either one of these, the diagnostic scanner will show codes that could cause an engine shutdown.

Some of the signs of a failed G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when you're in gear. If you have any of these issues it is likely that your sensor is deteriorating and needs replacing. The good news is they are very cheap and readily available particularly in the case of an Bosch unit which is what we have. Alternately, GM's version this part would be an option.

5. Tachometer

A failing engine sensor could cause a myriad of issues in your car. It's a vital component of your audi key replacement's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor could cause the transmission to fail and other components in the car to be affected.

The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It sends an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to regulate the flow of fuel and boost and also to timigrate. It also relays it to the G5 Tachometer in instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see an average resistance of 1000 ohms between these two points. This is a standard component across the new audi key 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.