P0133 code on 98 Explorer 4.0 x engine

[Gary Sasinowski]

I have a 98 Explorer 2 wd with a 4.0 x engine with about 290,000 miles on it and my check engine light came on the other day. I just had it read and it came up with P0133 Bank 1 Sensor 1 circuit shows slow response. The auto parts store didn’t really offer any troubleshooting procedures for this code and I really couldn’t find anything on line, though most said to replace the bank 1 sensor 1 as a fix. As Eric says, troubleshoot the problem before just throwing parts at a problem hoping for a fix. How would i go about troubleshoot- ing this code? With the engine running would I disconnect the connector and check voltage across the sensor plug? From what I understand it should read about .5 volts and should be changing constantly or do I leave it connected and stick pins in the wire behind the connector and read it that way? Is there a resistance check for the sensor? Thanks for the help in advance.

Topic

[Gary Sasinowski]

Ok, I finally was able to replace the fuel pump on the Explorer and still no 02 sensor readings! I haven’t been able to check the fuel pressure on the new pump yet as I returned the test kit to the auto parts store. I took it on a long drive (mainly to put gas in it) to allow the system to hopefully reset itself and get some sensor readings. No dice. I wrote down all the readings from the obdII scanner so you can see all the variables. I don’t know if all scanners read in the same order or use the same abbreviations; this is the way my friend’s scanner reads (Centron from Harbor Freight).
DTC_CNT 0
FuelSys 1 CL
FuelSys 2 N/A
Load Pct 30.6
ETC 185
Shrt FT 1 % -100.0
Lng FT 1 % -100.0
Shrt FT 2 % -100.0
Lng FT 2 % -100.0
RPM 818
VSS 0
Spark Adv 10
IAT 120
TP 18.4
02B1S1 0
Shrt FT B1S1 -100.0
02B1S2 0
Shrt FT B1S1 -100.0
02B2S1 0
Shrt FT B2S1 -100.0

Does this info give anyone a better idea what is going on with my vehicle. In case anyone is wondering, the scanner is working properly; I connected it to my Lesabre and it gave sensor and FT readings. Thanks again.

[Gary Sasinowski]

I was finally able to get the fuel pressure checked after replacing the fuel pump and the readings were identical to my old pump, 28 psi. The manager at the parts store where I borrowed the fuel pressure tester was wondering if the ecm was going bad, he thought I should be getting some kind of reading off the o2 sensors. I disconnected the big electrical connector that sits under the upper manifold and sprayed it with electric contact cleaner and still no readings. I also checked the connectors at the ecm and they were solid and dry. Is there a way to test the ecm to see if its going bad? Thanks.

[Andrew Phillips]

Before condemning the ecm, which should always be the last resort, the next step is to check the fuel injectors. Even with a bad ecm you should be able to obtain full fuel pressure, less than 30 is below spec and indicates there is still a fault in the fuel system. Have you checked the fuel injectors for leaky or sticking nozzles?

[Gary Sasinowski]

No I haven’t checked the injectors, will do that when my son is off work next. Thanks.

[Gary Sasinowski]

Ok, sorry about the large gap of time in closing up this thread but several things have happened since my last post. About 1 month ago, the Explorer died on me while out shopping and I couldn’t get it started. Long story short, I ended up having to be towed back home and have a mechanic look at it. Turns out that the PCM was bad; it was the first one he had seen fail on an Explorer in all his years as a mechanic and spent a couple of hours troubleshooting other things because he couldn’t believe the PCM failed…he didn’t charge me for all the extra time either. After he changed the PCM I decided to check the engine readings with an OBD II scanner to see if the O2 sensors and fuel trim readings were now showing up. To my surprise they still weren’t showing! I was dumbfounded, I thought for sure that the ECU would fix the problem but it didn’t. Frustrated, I looked at the wire connections thinking I had either broken wires, ground issue, bent pins, etc but they all checked out. I went on-line to look up how fuel trims worked and for wiring schematics and happened to come across a topic of “no O2 sensor readings and fuel trim readings at -100” on 1997 Explorer, the very problem I was having, on the “Great Explorations” forum. Turns out, the moderator came up with the solution: there is a software conflict with that year Explorers re: the O2 sensor and fuel trim readings and OBDII code readers! Here’s the statement Actron gave re: this problem: “We are aware of this problem. This is a common issue when using a global OBD II scanner on some ’97 Ford light-duty vehicles. It is a software issue in the vehicle (The same results occur on the FORD NGS tool if set to scan in global mode), and cannot be rectified. The tool would need enhanced scanning capabilities, which this tool does not. You would need something along the lines of a OTC Nemisys (wwwotctools.com 1-800-533-6127). So it seems after reading this that there was nothing really wrong with my vehicle after all! I spent a lot of money on this issue and replaced several parts that probably didn’t need to be changed; fortunately I kept the old parts just in case. Hopefully my situation will help someone else out with that has this particular problem. I’m still going to try to get these systems read on a computer when I get some spare $$”s just to satisfy my curiosity of what the readings actually are. Thanks for all the help and suggestions, you guys are great! Again, I apologize for the delay in finishing this thread.

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