Mechanics

O2 CODE OVERLOAD

1997 Ford Ranger • 4.0L V6 4WD Automatic •

Hi, I've been trying to pinpoint the root cause of the codes I've been receiving. The check engine light is on and I'm getting the following codes:

P1132 Lack of Upstream Heated Oxygen Sensor Switch Bank 1
P0141 O2 Heater Circuit ( Bank 1 : Sensor 1 )
P0155 O2 Heater Circuit ( Bank 2 : Sensor 1 )
P0135 O2 Heater Circuit ( Bank 1 : Sensor 1 )
P1152 Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2

I had an O2 sensor go bad on me a couple years ago, replaced it and was groovy. Now I'm showing 2 are bad. Including the one I previously changed? I'm a little skeptical it's the sensors this time.

I've checked:
+ Visual inspection of wires and terminals looked good.
+ The fuse is good. (15amp under the hood).
+ Voltage is getting to the sensors, Pin 1 & 2. I'm not sure what I would be checking for on pins 3 & 4, they lead right back to the PCM.
+ The MAF, looked super clean.
+ Recently did a service with clean air filter/oil, fuel filter, plugs & wires
+ Throttle body is clean
+ Did not find a vacuum leak (with a butane test hoping I wouldn't burst into flames)
--- I did find a couple small hoses from the EGR system that were suspect and changed them out.
+ Other than that, the EGR system was clean and functioned properly.
+ Checked the fuel pressure (was on target according to chiltons)
--- Not a fan of chiltons, are there better alternatives? Haynes seems a little better. Did I just answer my question or is there an even better one?

Though I did have voltage to the O2 sensors, this fancy live data scan tool says the voltage amplitude to HO2S11 & HO2S21 was 0.00. The switchpoint for both upstream and downstream tested OK at.45 &.50 respectively.

Also, I was seeing FUELSYS1 - Open Loop Fault, then it stopped that and was switching from OL to CL with no fault.

This is from the live data sitting at idle.
SHRTFT1(%) = -100.00
SHRTFT2(%) = -100.00
LONGFT1(%) = -100.00
LONGFT2(%) = -100.00

O2B1S1 = 0.000 v
SHRTFTB1S1(%) = -100.00
O2B1S2 = 0.000 v
SHRTFTB1S2(%) = -100.00
O2B2S1 = 0.000 v
SHRTFTB2S1(%) = -100.00

Here is the Freeze Frame data:
FUELSYS1 = OL-Fault
LOAD_PCT = 47.5
ECT = 188 f
SHRTFT1 = 3.9
LONGFT1 = 0.0
SHRTFT2 = 3.9
LONGFT2 = 0.0
RPM = 1838
VSS = 40mph

I'm no doctor, but the only idea I have left is that it is the PCM's fault and I need to replace it. But I would not be offended when you point out my ignorance and point out the real offender.

Any help is much appreciated.
Thanks,
Chris
Avatar
Cfoster20
June 17, 2014.




Codes 141-155-135-152 shown together may indicate wiring fault see diagram of H2O connector With DVOM measure voltage KOEO at each Pin also OHM check ground pin to ground. Let me know results. Have you ruled out any intake air plenum leaks and exhaust leaks? Also exhaust restriction? And how does it run? And do codes return after erased?


Docfixit
Jun 17, 2014.
Hey Doc, I appreciate your quick response. I was finally able to do a little probing.

I checked the wiring and here's what I was reading.
VPWR = 11.81
SIGRTRN = -18.5
HO2SSIG = -14.8
Ground pin has good ground.

Same codes come back after an erase.

As far as the live data I was getting, I'm not convinced the scan tool was being honest with me. I think it is not reading the voltage and fuel trim in the live feed.

The Freeze Frame told a bit different story.
FUELSYS1 OL-Fault
SHRTFT1 9.4%
LONGFT1 0.0%
SHRTFT2 9.4%
LONGFT2 0.0%

I ran some of the diagnostic utilities and the O2's all passed their voltage tests but there were some failures here as well: Not10 front switch Ratio Bank 2 (FAIL)
Test 1024.0
MIN
Max 0.8

Delta Pressure for Downstream Hose Test (FAIL)
Test 0
MIN
Max -506

Cylinder Events Tested (FAIL)
Test 84.48
MIN
MAX 0.00

As far as how it's running, you can really tell it's running rich from the exhaust itself. Cold start it stumbles a little then the idle smooths out a little after a couple minutes.

On the road there is not as much power as before and fuel efficiency is terrible. When you get up to around 35/40 mph she'll stumble. Seems to be a consistent sore spot.

I'll check again for leaks/restriction. I must have missed something.

I appreciate your time.
AD


Tiny
Cfoster20
Jun 25, 2014.

AD