View Full Version : Fuel Pump Replacement / Multiple Short to Ground codes

09-05-2018, 09:12 AM
A buddy's car died while merging onto the highway. It's a 2001.5 A4 2.8Q (30v), with ~195k miles. Towed the car home, ran codes:

P0155 - 02 Sensor Heater Circuit Bank 2 Sensor 1
P1411 - Sec.Air Inj.Sys.,Bank 2 Flow too Flow
P1423 - Sec.Air Inj.Sys.,Bank 2 Flow too Low

Aside from those codes, car tries to turn over but did not seem to have either fuel or spark. Found that fuel pump wasn't priming on start. Replaced fuel pump. Car will now start, but idols extremely rough for about 60 seconds, then dies. Additionally, it's now throwing 9 different "Short to Ground" codes and a Mass/Volume Air Flow code:

P1425 - Tank Vent.Valve Short to Ground
P1472 - EVAP Emission Contr.LDP Circ Short to Ground
P1435 - Sec.Air Inj.Sys.Pump Relay Circ. Short to Ground
P1530 - Camshaft Control Circuit Short to Ground
P1421 - Sec.Air Inj.Valve Circ Short to Ground
P1121 - 02 Sensor Heater Circ.Bank 2-Sensor2 Short to Ground
P1117 - 02 Sensor Heater Circ.Bank 1-Sensor2 Short to Ground
P1115 - 02 Sensor Heater Circ.Bank 1-Sensor1 Short to Ground
P1119 - 02 Sensor Heater Circ.Bank 2-Sensor1 Short to Ground
P0102 - Mass or Volume Air Flow A Circuit Low

The fuel pump relay appears to be fine.
Fuses #29 and #34 are both good.
The ground wires on the fuel pump were double checked.
MAF sensor has been cleaned with MAF cleaner.
Battery and alternator tested fine.

09-05-2018, 11:03 AM
Have you checked all the grounds?

Sent from my iPhone using Tapatalk

09-05-2018, 11:38 AM
Have you checked all the grounds?

Sent from my iPhone using Tapatalk

Yes, all of the relevant ground connections have been checked.

09-05-2018, 02:21 PM
Here's a video demonstrating the idle:


09-06-2018, 07:34 AM
Sounds horrible!

I guess I would go through basics - check fuel pressure, check injector pulse, check each spark plug, check timing using vagcom. Did you try clearing the codes to see what comes back?

Sent from my iPhone using Tapatalk

09-06-2018, 12:13 PM
No! It was running fine! Just check basics. See what you can find. Maybe fuel pressure first?

Sent from my iPhone using Tapatalk

A4 2.5TDI
09-06-2018, 12:23 PM
Don"t torch the car B5 audis are great cars. what fuel pump did you instal it could be that it has lower fuel pressure then the one you replaced

09-06-2018, 12:53 PM
Yes you can test fuel pressure with a fuel pressure tester. You can check injector pulse with a stethoscope.

Sent from my iPhone using Tapatalk

09-06-2018, 01:52 PM
"Short to Ground" codes almost always mean the fuse is blown for that circuit. The ECU is expecting to sink the current for each accessory (MAF, O2 sensor, etc) to ground internally. When it sinks zero current, it assumes there is already a "short to ground" upstream in the circuit. The situation is most commonly encountered when a circuit or device fault has caused the supply fuse to blow.

Every code you listed points back to Fuse #34 (15 amp). This would be the Green/Yellow wire to all of the accessories that are throwing codes. Visual inspection of the fuse is not good enough. Make sure Fuse #34 has battery voltage during cranking/running. If that is good, make sure the wire itself has 12 volts while running/cranking. It should have power whenever the fuel pump is running. You can, for example, test the Green/Yellow wire at the MAF sensor location.

09-07-2018, 03:50 PM
Judging by the video itís either starving for fuel or you have a pretty big vacuum leak.Are you sure all the intake hoses are tight?No leak on the intake side of the engine.Also check any vacuum lines on the engine.

Sent from my iPad using Tapatalk

09-12-2018, 03:38 PM
I keep watching the video trying to decide if it's normal how much that voltmeter is moving while the idle is bouncing up and down.

09-20-2018, 03:57 PM
If it were me I would check all the relays and find the big ground cable that hooks up to the negative terminal on the battery to make sure of no excessive corrosion. Also could be your cats being clogged up or o2 sensors getting old

Sent from my SAMSUNG-SM-G920A using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)