How to Replace an audi tt key case G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission, above the flywheel gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU uses this information to regulate the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

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

If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate a chain stretch or a jumpy chain link in the upper timing chain. The code won't appear without the additional information supplied by other sensors (G4 or G40).

Testing can be a bit difficult because there are two connector pins and they serve different purposes but the best method to test it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms when the sensor is in full operation. Look replacement key for audi a4 evidence of coolant or oil in the connector bay if you have problems with this part.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at maximum speed, i noticed a huge decrease in power. It was like the engine had run out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, 3 were drenched in gazoline, the 4th one was dry. I put a piece of tissue over each hole in the injector and when i start the engine without sparks, the ones with gazoline jump right out. The 4th one stays closed. I checked the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got 0ohm. I'm assuming that the issue is in another location.

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 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.

I'm not certain what to do, but i think i've pretty much completely ruled out all other possibilities. However, i'm afraid that i might have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or a parts store. It is simple 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 up). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that needs to know the position and speed of the crankshaft to make a decision about fuel injector timing etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

A damaged G28 sensor could cause an inaccurate speed counter for your gearbox, a gearbox that shifts faster than normal, and/or a misfire while in gear. If you have any of these problems, it is most likely that your sensor is deteriorating and needs replacing. They are cheap and easy-to-find especially when they're a Bosch sensor like ours. Alternately, the GM version of this unit is also a good option.

5. Tachometer

A failing engine sensor could cause a number of problems within your vehicle. It's a crucial component of the transmission in your Audi a5 Key fob, as it transmits information to the ECU about how fast or slow the engine of the car is spinning. When this sensor fails, it will cause problems for the transmission as well as the rest of the car's components.

The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU utilizes this signal to regulate fuel and boost, and also timig. It also relays it to the G5 Tachometer in instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 and pin T26a/12. It should show around 1000 ohms of resistance between these two points. This part is common across the audi keyfob 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU So, you may find some good ones in wrecking yards.