How to Replace an audi tt key 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 edges of the transmission, above the flywheel ring gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.

The sensor is used to connect the G40 Camshaft position Sensor. The ecu must 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 alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper timing chain. However, the error code won’t appear on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging since there are two connector pins and they serve different purposes however the best method to test it is by measuring resistance between the sensor and the ECU. When the sensor is operational, it should read approximately 1000 ohms. If you’re having issues with this part, check for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had a big cut in power like the engine is running out of gas or the injectors are not firing anymore. I pulled out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was unclean. I placed a 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 inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero Ohm. Therefore, i think the issue is elsewhere.

I also tried to reset the PID but with no luck. The car will start when the G28 is unplugged, and it runs fine with the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even when unplugged, still shows an ice temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I’m not certain what to do, as i think i’ve pretty much completely ruled out all other possibilities. I’m afraid i may have missed something. Please let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, audi a3 key Fob replacement (Letsbookmarkit.com) and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. It is simple to test them by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector’s side up) and 2 (2nd from left on the black connector’s end). They should be infinite ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines requires to know both the speed and Audi Spare keys position of the crankshaft to make decisions regarding fuel injector timing, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.

A damaged G28 sensor could cause an inaccurate speed counter for the gearbox and a gearbox which shifts more quickly than normal, or a misfire in gear. It is probable that the sensor is failing and needs to be replaced if you notice any of these symptoms. The good thing is that they are very cheap and easy to find particularly when you’re looking at the Bosch model, which is what we have. Alternately, GM’s version this part would be an option.

5. Tachometer

A malfunctioning engine sensor can cause a number of problems in your vehicle. It is an important part of the transmission in your audi a3 keys because it relays information to the ECU about how fast or slowly the engine of the car is spinning. If this sensor fails, it will affect the performance of the transmission and the other car’s components.

The G5 engine sensor is located at the outskirts of the transmission, just above the flywheel ring. It transmits signals via gray wire to ECU pin T55/49. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should observe around 1000 ohms of resistance between these two points. This is the same across the audi tt key programming 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 DU So, you may find them in wrecking yards.