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 located at the edge of transmission, above the flywheel gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through an uncolored wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors according to the situation.
If this sensor fails the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. The code won't show without the additional information provided by other sensors (G4 or G40).
It can be a bit difficult to test as there are various pins on the connector and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when it is in full operation. Examine for evidence of coolant or oil in the connector bay if you are experiencing problems with this part.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive drop in power. It was as if the engine was running out of gas. Or my injectors weren't firing. I took out the spark plugs this morning, 3 were soaked in gasoline, and the 4th was dry. I placed a tissue over each injector hole, and when I start the engine with no sparks, the 3 with gazoline jump out. The 4th one remains shut. I tested the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I'm assuming that the issue is somewhere else.
I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However, the intermittent misfire problem continues to occur at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c even when i unplug it. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, but i feel i have pretty much eliminated everything else. I'm worried that i might have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. Testing them is easy to do - just put your DMM in resistance mode and measure 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 ADU) engines needs to be aware of the position and speed 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 either of these sensors go wrong, you will receive codes on the diagnostic scanner which can lead to engine shutdown.
Some of the signs of a malfunctioning G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when you are in gear. If you experience any of these issues, it is likely your sensor is going bad and needs replacing. They're inexpensive and easy to locate especially in the case of an Bosch sensor like ours. If replacement audi key prefer, GM's version of this component is a good option.
5. Tachometer
A failing engine sensor could cause a myriad of issues within your vehicle. It is a crucial part of the Audi's transmission because it communicates to the ECU about how fast or slow the vehicle's crankshaft is rotating. This sensor can cause the transmission to fail and other car components to be affected.
The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to regulate fuel and boost, as well as timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. You can also examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should detect an average resistance of 1000 ohms in these areas. This is a common feature across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 DU You may also find some good ones in wrecking yards.