How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49) and then to the tachometer located in 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 using an uncolored wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.

If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging because there are two pins for the connector and they have different functions but the best way to test it is by measuring resistance between the sensor and the ECU. It should read around 1000 ohms if the sensor is operating at its maximum. If you're having issues with this component, look for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll, i experienced a big cut in power like the engine is running out of gas or the injectors aren't firing at all. I pulled out the spark plugs this morning and found that 3 were soaked in gasoline, and the 4th was dry. I put tissue over each hole in the injector Audi key Replacement cost and when I start the engine with no sparks, the 3 that have gazoline pop right out. The 4th one stays shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I'm assuming that the issue is somewhere else.

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 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar while the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, as i feel i have pretty much ruled out everything else. I'm afraid i may have missed something. If anyone has any suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. Testing them is easy to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that must know the speed and position 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 you are experiencing issues with either of these, the diagnostic scanner will show codes that could lead to an engine shutdown.

A failing G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, or a misfire in gear. If you have any of these problems, it is most likely that your sensor is deteriorating and requires replacement. They're inexpensive and easy to locate particularly when they're an Bosch unit like ours. Alternatively, the GM version of this component is also a good choice.

5. Tachometer

A faulty engine speed sensor could be the reason behind a slew of issues in your vehicle. It's an essential component of the transmission in your audi a3 key fob because it relays information to the ECU on how fast or slowly the car's engine is turning. This sensor can cause the transmission to malfunction and other car components to be affected.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU utilizes this signal to regulate the flow of fuel and boost as well as timig. It also sends it to the G5 Tachometer in instrument cluster. You can test for Audi Key Replacement Cost sensor failure by examining the continuity from the sensor to the tachometer. Also, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see a resistance of approximately 1000 ohms between these points. This is a common part across the audi key Replacement cost 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.