How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is situated at the edge of transmission just above the flywheel gear. It sends a signal to the ECU via the grey wire (T55/49) and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has 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 an error code P00160. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. audi a3 key could also indicate a chain stretch or a jumpy chain link in the upper chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).
Testing can be a bit difficult since there are two pins for the connector and they perform different functions however the best method of testing it is by measuring resistance between the sensor and the ECU. If the sensor is functional, it should read approximately 1000 ohms. Check for evidence of coolant or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed I noticed a significant reduction in power. It was like the engine was running out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs. Three were drenched in gazoline, the fourth one was dry. When I start the engine without sparks i put tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th stays closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. I think the issue is in another location.
I also tried to reset PID but without success. The car is able to start when the G28 is disconnected and runs fine when it is plugged in however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when unplugged, still shows an ice temperature 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 believe that I've all other possibilities out. However, i'm afraid that i might have missed something. If anyone has any ideas please chime in! 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 works on the 80,100,200, UrS, and RS2 vehicles. It is easy to find an extra in a wrecking shop or a parts store. It is easy to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of the crankshaft to make decisions regarding fuel injector timing, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes wrong, you will receive codes on the diagnostic scanner that could cause engine shut down.
A malfunctioning G28 sensor could result in an inaccurate speed counter for your gearbox and a gearbox which shifts faster than normal, and/or a misfire in the gear. If you experience any of these issues, it is likely that your sensor is deteriorating and should be replaced. They're inexpensive and easy to locate, especially if they're a Bosch unit like ours. Alternately, the GM version of this component is also a good option.
5. Tachometer
A damaged engine sensor could cause a myriad of issues in your car. It is a crucial part of the Audi's transmission since it relays information to the ECU about how fast or slow the car's crankshaft is turning. If the sensor fails, it can affect the performance of the transmission as well as the rest of the car's components.
The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It transmits an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU then uses and processes this signal to control the flow of fuel, timig and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. There should be a resistance of approximately 1000 ohms between these two points. This is a standard part across the Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.