20 Myths About Audi G28: Debunked
20 Myths About Audi G28: Debunked
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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 edge of transmission just above the flywheel gear. It sends a signal to the ECU via the grey wire (T55/49), then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via an uncolored wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.
The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors in the right way.
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 tricky as there are two different pins for the connector and they have different functions but the best method of testing it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms when the sensor is in full operation. If you are having problems with this sensor, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a significant drop in power. It was as if the engine had run out of gas. Or, my injectors were not firing. This morning i pull out the spark plugs, three were drenched with gazoline the fourth was dry. When I crank the engine without sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline jump out but the 4th one stays shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is elsewhere.
I also tried to reset the PID without success. The car is able to start when the G28 is disconnected and runs fine when it is plugged in however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when unplugged, still shows a temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I don't know what to do. I think I've eliminated everything else. I'm worried that i might have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sender is identical to the G4 and they both work in the 80 100 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. It is easy to test them - simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft to make decisions regarding timing of the fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor more info (G28). If you encounter a problem with either of these sensors, the diagnostic scanner will display codes that could cause an engine shutdown.
The signs of a failed G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal, and/or a misfire when you are in gear. If you experience any of these problems, it is most likely that your sensor is deteriorating and needs replacing. The good thing is that they are quite affordable and easily accessible, especially in the case of the Bosch sensor, like ours. Alternately, the GM version of this component is also a good choice.
5. Tachometer
A faulty engine speed sensor could be the cause of a slew of problems in your car. It's a vital component of the Audi's transmission since it relays information to the ECU about how fast or slow the car's crankshaft is spinning. If the sensor fails, it will disrupt the performance of the transmission and the rest of the car's components.
The G5 engine speed sensor is situated on the edge of the transmission, above here the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU uses this signal to control the flow of fuel and boost and also timig. It also read more sends it to the G5 Tachometer located in the 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 more info 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. You should see a resistance of approximately 1000 ohms in these areas. This part is common across the Audi 80-100-200-RS2 model, ranging from the 1985 MC all the way up to more info the 1997 UrS AN and the 1995 RS2 Du So, you may find some good ones in wrecking yards.