How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is located near the transmission's edge just above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer on 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 a signal via the grey wire to pin T55/49. The ECU uses this information to regulate boost and fuel. It also sends a signal to the G5 tachometer in the instrument cluster.
The sensor is used to connect the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors accordingly.
If this sensor fails the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating the chain is stretched or a jump link on the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit tricky as there are two different connector pins, and they perform different functions but the most effective method of testing it is by measuring resistance between the sensor and the ECU. It should read approximately 1000 ohms when it is in full operation. Examine for signs of coolant or oil in the connector bay if you have issues with this component.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, I experienced massive power loss like the engine is running out of gas or injectors aren't firing any more. This morning i pull out the spark plugs, 3 were drenched with gazoline the fourth one was dry. When I start the engine, there are no sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stays shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero Ohm. So i assume the problem is somewhere else.
I also tried to reset the PID but with no luck. The car is able to start if the G28 is unplugged and it runs perfectly when it is connected 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 0.
I'm not sure what to do. I believe that I've eliminated everything else. I'm afraid i may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is the same as the G4 and both are used in the 80 100, 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local 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 end facing up). They must be infinite ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. audi a1 key makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues 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 gearbox speed counter, a gearbox that shifts faster than normal, and/or an unfire when in the gear. If you have any of these issues, it is most likely that your sensor is going bad and requires replacement. They are cheap and easy-to-find especially in the case of a Bosch unit like ours. Alternately, the GM version of this part is also a great option.
5. Tachometer
A faulty engine speed sensor could be the reason behind many problems in your car. It is an important part of the transmission in your Audi since it sends information to the ECU regarding how fast or slow the car's engine is turning. This sensor can cause the transmission to malfunction and other components of the car to be affected.
The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends signals via gray wire to ECU pin T55/49. The ECU uses this signal to regulate fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer inside the instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. You can also 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. You should detect a resistance of approximately 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and 1995 RS2 DU You may also find some good ones in wrecking yards.