How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask hauto Your Own Question
hauto, Saturn Technician
Category: Saturn
Satisfied Customers: 2727
Experience:  worked on saturns for 7 years, in a saturn dealership. saturn factory trained and ceritfied.
Type Your Saturn Question Here...
hauto is online now
A new question is answered every 9 seconds

2003 saturn l300: 2.3 liter one..fuel trim..same code

Resolved Question:

i have a 2003 saturn L200 with the 2.3 liter engine with code po172B bank one system to rich and fuel trim rich with the same code
Submitted: 7 years ago.
Category: Saturn
Expert:  hauto replied 7 years ago.

Po172 is not always an indication of a rich condition. the following diagnostic aids will help you get an idea on what it could be. You need a scan tool that can read voltage data from the o2 sensor to determine if their faulty.

DTC P0172 indicates the engine is running rich. The following are possible causes of a rich air/fuel mixture:

  • Fuel pressure high
  • Fuel injector(s) leaking
  • HO2S-1 contaminated
  • Vacuum leak around MAP sensor
  • EVAP purge solenoid stuck open
  • Restricted exhaust or restricted air induction

To verify the system is running rich, use Scan tool to monitor HO2S-1 and HO2S-2. If both sensors are above 600 mV , the system is running rich and the oxygen sensors are probably not at fault.


Customer: replied 7 years ago.
I have a scan tool so I just need to read live data then when you push on the gas it revs very high and you go nowhere that is why I thought it might be a transmission problem so I had them service the transmission and it was good for a weak or so and the light came back on this is not my car it is a friends and I am trying to fix it for them
Expert:  hauto replied 7 years ago.

No this code has nothing to do with the transmission, usually when you clear it it does not come back right away.

If you read o2 sensor voltage with your scanner and they read above 600mv then the system is running rich and the o2 sensor are not the problem, then you look for a vacuum leak, exhaust leak. if you find none then one of the injectors may be leaking.

If the HO2S-1 AND 2 read below 600mv then they would be the faulty part.

Customer: replied 7 years ago.

how can you tell if one of the injectors is leaking I will try that on reading the oxygen sensor voltages though and see what they read first

Expert:  hauto replied 7 years ago.

Well. the easy way but not real efficient is if the O2 sensors are reading within the specs, and there are no vacuum or exhaust leaks. and code po172 is present that's an indication of a rich condition.

there are two ways to test the injectors,

1. to remove them out of the intake and place a dry paper under them for a while

then if part of the paper becomes wet under an injector then that injector is leaking.

2. You can do an injector balance test using a good scan tool.

Customer: replied 7 years ago.

bank 1 sensor

rich-lean thres volt 0.555 volts

lean - rich thres volt 0.530 volts

low voltage switch line 0.350 volts

high voltage switch time 0.650 volts

rich lean switch time 0.032 volts

lean rich switch time 0.024

Expert:  hauto replied 7 years ago.

If those are active readings of the senor then the senor is not reading within specs

if there are no exhaust leaks around the senor then replace the senor.

hauto and other Saturn Specialists are ready to help you