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How to Replace an audi tt 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 edge of the transmission just above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49), then 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 G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via a grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indicator to the G5 Tachometer in instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors accordingly.

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

It is a little tricky to test since there are various pins on the connector and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is fully operational, it should read approximately 1000 ohms. Look for signs of coolant, or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced massive power loss like the engine is running out of gas or audi tt Key injectors are not firing anymore. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was dry. I put tissue over each injector hole, and when I start the engine without sparks, the 3 with gazoline jump right out. The 4th one stays closed. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got 0ohm. Therefore, i think the issue is somewhere else.

I also tried to reset the PID but without success. The car is able to start when the G28 is not plugged in and runs fine when it is plugged in but it still has intermittent misfire issues at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.

I'm not sure what to do. I feel like i've pretty much eliminated everything else. I'm concerned that i may have missed something. If anyone has any ideas please let me know! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style sender is identical to 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 at a parts store. It is easy to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines needs to know both the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these sensors, the diagnostic scanner will show the codes that could trigger an engine shut down.

A malfunctioning G28 sensor could result in an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire while in the gear. It is possible that the sensor is failing and requires to be replaced if you notice any of these signs. The good news is they are very cheap and easy to find particularly when you're looking at an Bosch model, which is what ours are. If you prefer, GM's version of this part is a good option.

5. Tachometer

A faulty engine speed sensor could be the cause of many problems in your car. It's an essential component of the transmission of your audi spare key since it sends information to the ECU about how fast or slow the engine is spinning. When this sensor fails, it could disrupt the performance of the transmission and the rest of the car's components.

The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through an uncolored wire. The ECU uses this signal to regulate the flow of fuel and boost as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should detect a resistance of approximately 1000 ohms in these areas. This is a common feature across the audi a1 key 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and 1995 RS2 Du You may also find good ones in wrecking yards.