Help with OBD diagnostics

[rick-l]

Am I interpreting this right? It is a 4 cyl so there is no bank 2

• Long Term Fuel Trim Bank One: 17.94 % ...... It is adding much more fuel than it thinks it should
• System Too Lean .... Intake air leak?
• Absolute Throttle Position: 19 % Engine RPM: 753 r/min ........ HUH?

Freeze Frame data

MIL:
On
Diagnostic Trouble Codes
P0171
System Too Lean (Bank 1)
Freeze Frame (Frame 0) for DTC P0171
Absolute Throttle Position:
19 %
Air Flow Rate From Mass Air Flow Sensor:
0.46 lb/min
Calculated Load:
20 %
Coolant Temperature:
196 F
Engine RPM:
753 r/min
Fuel System Status Bank One:
Closed Loop
Fuel System Status Bank Two:
Not Reported
Ignition Timing Advance for #1:
7.0 deg
Intake Air Temperature:
46 F
Intake Manifold Absolute Pressure:
8.6 in.hg
Long Term Fuel Trim Bank One:
17.94 %
Short Term Fuel Trim Bank One:
-1.56 %

[lm6y]

What kind of car?

"Generally" a lean condition is a bad o2 sensor, or a fuel pump. Is the scanner not giving you an o2 sensor reading for the freeze frame data ?

It could be a vacuum leak too, as you said.

[rick-l]

It is a Chevy Colorado

Inspection/Maintenance Monitors Status




Name
Status

Misfire Monitoring
Complete

Fuel System Monitoring
Complete

Comprehensive Component Monitoring
Complete

Catalyst Monitoring
Complete

Heated Catalyst Monitoring
Not Supported

Evaporative System Monitoring
Complete

Secondary Air System Monitoring
Not Supported

A/C System Refrigerant Monitoring
Not Supported

Oxygen Sensor Monitoring
Complete

Oxygen Sensor Heater Monitoring
Complete

EGR System Monitoring
Not Supported





--------------------------------------------------------------------------------





Monitored Test Results (Mode $06)




Test ID
($05) Oxygen Sensor Monitoring
Value
425.000
Min
0.000
Max
2048.000
Units
mV




Test Description
($01) Rich to Lean Sensor Threshold Voltage - Bank 1 Sensor 1




Test ID
($05) Oxygen Sensor Monitoring
Value
425.000
Min
0.000
Max
2048.000
Units
mV




Test Description
($02) Lean to Rich Sensor Threshold Voltage - Bank 1 Sensor 1




Test ID
($05) Oxygen Sensor Monitoring
Value
350.000
Min
0.000
Max
2048.000
Units
mV




Test Description
($03) Low Sensor Voltage for Switch Time Calculation - Bank 1 Sensor 1




Test ID
($05) Oxygen Sensor Monitoring
Value
650.000
Min
0.000
Max
2048.000
Units
mV




Test Description
($04) High Sensor Voltage for Switch Time Calculation - Bank 1 Sensor 1




Test ID
($05) Oxygen Sensor Monitoring
Value
39.375
Min
0.000
Max
1024.000
Units
msec




Test Description
($05) Rich to Lean Sensor Switch Time - Bank 1 Sensor 1




Test ID
($05) Oxygen Sensor Monitoring
Value
32.484
Min
0.000
Max
1024.000
Units
msec




Test Description
($06) Lean to Rich Sensor Switch Time - Bank 1 Sensor 1




Test ID
($05) Oxygen Sensor Monitoring
Value
249.000
Min
141.000
Max
0.000
Units
Switches




Test Description
($07) Rich to Lean Switches - Bank 1 Sensor 1




Test ID
($05) Oxygen Sensor Monitoring
Value
253.000
Min
141.000
Max
0.000
Units
Switches




Test Description
($08) Lean to Rich Switches - Bank 1 Sensor 1




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
0.200
Min
0.100
Max
6553.500
Units
sec




Test Description
($01) EVPD Canister Vent Restriction Test 1




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
5.001
Min
0.000
Max
31.999
Units
inH20




Test Description
($42) Engine Off Natural Vacuum Tests




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
9.110
Min
0.000
Max
65.535
Units
Liters




Test Description
($13) EVAP Vacuum Pressure Decay (Weak Vacuum) Test




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
0.000
Min
0.000
Max
0.000
Units
Unitless




Test Description
($04) Undocumented CID




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
600.000
Min
600.000
Max
0.000
Units
Unitless




Test Description
($07) Undocumented CID




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
0.000
Min
-3276.800
Max
3276.700
Units
inH20




Test Description
($48) EVPD Purge Vacuum Fail Test




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
0.000
Min
0.100
Max
255.996
Units
Ratio




Test Description
($0A) EONV .020" Small Leak Test




Test ID
($0A) Evaporative System Monitor 0020" Leak
Value
0.051
Min
0.100
Max
255.996
Units
Ratio




Test Description
($0B) EONV Vacuum Rezero Test




Test ID
($0C) Catalyst Efficiency Idle Monitor
Value
-6.991
Min
-32.768
Max
32.767
Units
sec




Test Description
($60) Idle Catalyst Efficiency Test - Bank 1




Test ID
($0E) Oxygen Sensor Heater Monitoring
Value
0.000
Min
0.000
Max
45.000
Units
Samples




Test Description
($11) Oxygen Sensor Heater Current Samples Outside Threshold (X/Y Samples Test) - Bank 1 Sensor 1




Test ID
($0E) Oxygen Sensor Heater Monitoring
Value
0.000
Min
0.000
Max
45.000
Units
Samples




Test Description
($12) Oxygen Sensor Heater Current Samples Outside Threshold (X/Y Samples Test) - Bank 1 Sensor 2

[djmcmath]

Too lean could very well be a vacuum leak post-MAF. Try the old carb cleaner trick to see if you can identify anything. If that fails, it isn't necessarily not a vacuum leak, it could still be one that's hard to find. Fuel pump starting to fail would cause fuel pressure to be less than calculated, depending on where your system senses pressure at. Oxygen sensors typically tell you when they're bad, don't they? I know that mine gave "out of range" errors when they started going out.