How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located near the transmission's edge over the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer within 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 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 indication to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also where the camshaft lies to trigger the spark and injectors.

If this sensor fails the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain stretching or a jump link on the upper timing chain. However the code will not 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 way to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should read approximately 1000 ohms. If you're experiencing issues with this sensor, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge decrease in power. It was as if the engine had run out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs. Three were drenched with gazoline the 4th one was dry. When I crank the engine with no sparks, i place a tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th stay closed. I tested the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. I think 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 connected. However the intermittent misfire issue persists at higher RPM. The coolant sensor (G62) even when it is unplugged, shows an ice check here temperature of -49c. Also i noticed that the gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when i rev the engine.

I'm not sure what to do, i believe that i've eliminated everything else. However, i'm afraid that I may have missed something. If anyone has any suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter is identical 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. Test them out to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black end of the connector). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft in order to make a decision about timing of the fuel injector, for example. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will display the codes that could trigger an engine shutdown.

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

5. Tachometer

A failing engine sensor could cause a number click here of problems within your vehicle. It's an essential component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. This sensor could cause the transmission to malfunction and other components of the car to be affected.

The G5 engine speed sensor is located 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 control the amount of here fuel and boost, and also timig. It also sends it to the G5 Tachometer inside website the instrument cluster. You can test for sensor failure by checking 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 more info [79]) and between pin T6a/1 and pin T26a/12. You should detect the resistance to be around 1000 ohms in these areas. This is the same across the Audi 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 might find some good ones in wrecking yards.