Notes

The Biggest "Myths" Concerning Audi G28 May Actually Be Right
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 situated at the edge of transmission over the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49), then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the outside of the transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging since there are two pins for the connector and they have different functions but the most effective method of testing 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 are having problems with this component, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll i had a big cut in power like the engine is out of gas or the injectors aren't firing at all. I took out the spark plugs this morning, three were soaked in gasoline, and the 4th was dry. When I start the engine with no sparks i put tissue on the top of each of the injector holes and the 3 that were drenched in gazoline pop out, but the 4th one stays shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found 0ohm. Therefore, i think the issue is somewhere else.

audi spare key replacement tried to reset PID but without success. The car can start when the G28 is unplugged and runs fine when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.

I'm not sure what to do. I feel like i've pretty much ruled everything else out. But i am afraid i might have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump


The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and both function in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or at a parts store. It is simple to test them by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines needs to know the speed and position of the crankshaft to make decisions regarding fuel injector timing, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger the engine shutting down.

Some of the symptoms of a malfunctioning G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or a misfire when in gear. It is likely that the sensor is failing and needs to be replaced if you encounter any of these signs. They're inexpensive and easy to locate, especially when they're an Bosch unit like ours. Alternately, the GM version of this component is also a good choice.

5. Tachometer

A damaged engine sensor could cause a myriad of issues in your car. It's an essential component of your Audi's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is spinning. If this sensor fails, it could affect the performance of the transmission and the other car's components.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends signals via gray wire to ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, and also to timigrate. It also transmits it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Also, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. There should be an average resistance of 1000 ohms in these areas. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and 1995 RS2 Du So, you may find them in wrecking yards.

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