Audi G28 10 Things Id Like To Have Known Sooner
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 situated near the edges of the transmission just above the flywheel ring gear. It transmits a signal to the ECU through 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, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using a grey wire. The ECU then uses this information to control 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 point to connect with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate a chain stretch or a jumpy chain link in the upper chain. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).
It's a bit tricky to test because there are various pins on the connector and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. When the sensor is fully operational, it should read around 1000 ohms. If you're having issues with this part, check for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive drop in power. It was like the engine had run out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the 4th was dry. When I start the engine without sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th stays shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got zero ohm. spare audi key 'm assuming that the issue is elsewhere.
I also tried to reset PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is zero.
I'm not certain what to do, i think i've pretty much completely ruled out all other possibilities. I'm worried that i might have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or a parts store. It is easy to test them - simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that has to know the speed and position of the crankshaft in order to make decisions regarding fuel injector timing etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go wrong, you will receive codes on the diagnostic scanner which can lead to engine shutdown.
A damaged G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire in gear. It is probable that your sensor is failing and needs to be replaced if you experience any of these signs. The good news is they are very affordable and easily accessible, especially in the case of the Bosch sensor, which is what ours are. Alternatively, GM's version of this part is an excellent choice.
5. Tachometer
A failing engine speed sensor could be the cause of a slew of issues with your vehicle. 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 spinning. This sensor can cause the transmission to fail and other car components to be affected.
The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to control fuel and boost, as well as timig. It also sends it to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. Also, you can check 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 a resistance of approximately 1000 ohms between these two points. This is the same across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN and 1995 RS2 Du You may also find some good ones in wrecking yards.
