My 94 cruiser was intermittently throwing code 28 for a heated o2sensor for cylinders 4-6. I would usually pull the EFI fuse and the code would clear for a while but I eventually decided to replace the o2sensor. I ordered the NTK part #244044 which is supposably the OE sensor for the 93-94's. After I installed it the CEL came on immiediatly and will not clear by pulling the fuse or battery terminal. I have checked voltages at the diagnostic port as well as the sensor and everything checks. The grounds are good, and the signal is being relayed to the ECU. The ECU does not appear to be malfunctioning and there are no other codes being thrown. I do occasionally have a low idle and a stutter in the exhaust possible indicating that it is running rich by I cannot tell what else could be the culprit. The FSM states code 28 solutions are o2sensor, wiring and ECU, but as far as my mechanic and I can tell there are no issues. I even order another o2sensor in case my replacement was a dud, but this did not solve the problem. Any ideas of where to check next? I know it's not a crucial failure but I cannot pass emissions with the CEL on so I need to find the solution. Any help or ideas would be greatly appreciated.
Code 28 issues (1 Viewer)
- Thread starter Overlander303
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
I would first verify that you have the correct part for your truck before going any further. There are Toyota parts experts on this forum.
You have 2 O2 sensors on your truck and they should be changed together.
It's also possible that the O2 connector(s) was damaged and/or corroded.
You have 2 O2 sensors on your truck and they should be changed together.
It's also possible that the O2 connector(s) was damaged and/or corroded.
Just a question, have you inspected the female pins inside the O2 sensor connector your having problems with? I had a problem with my passenger side O2 sensor on my 94. Come to find out water had gotten into that connector. Once i cleaned the water, and corrosion off of those pins that took care of my problem.
- Thread starter
- #4
I checked everything I could find, and from what I've seen the NTK #44044 is the correct OEM O2 sensor for the 94. I also read reviews before I ordered it from people that said they installed it on their 94 and it worked. I checked the female connection when I was testing the ground and it doesn't appear corroded or damaged. I used dielectric grease on the male end when I installed it just in case. This is why I posted the thread, every simple solution and every solution offered in the FSM has not worked and I'm at a dead end. I appreciate the replies. Thanks!
Dielectric grease is widely used as a sealant for spark plugs in gasoline or diesel engines, as well as on the gaskets of multi-pin connectors in the electrical systems of vehicles and boats. When used with spark plugs, it's applied to the rubber part of the plug wire. This helps the boot slide onto the plug's ceramic insulator and keeps dirt or moisture from contaminating the seal and disrupting the electrical current.
Besides being used to seal rubber covers on electrical connections, dielectric grease also prevents corrosion when applied directly to metal connectors. Though it works well for this purpose, it can sometimes cause a connection to stop working if not all of the grease is pushed out of the way between the points of contact inside the connector.
Please pay special attention to the last sentence of what was posted above, about the contacts not making a connection if all the grease is not pushed out of the way.
Besides being used to seal rubber covers on electrical connections, dielectric grease also prevents corrosion when applied directly to metal connectors. Though it works well for this purpose, it can sometimes cause a connection to stop working if not all of the grease is pushed out of the way between the points of contact inside the connector.
Please pay special attention to the last sentence of what was posted above, about the contacts not making a connection if all the grease is not pushed out of the way.
- Thread starter
- #6
Slight update, I found out the idle issue was caused by a dirty distributor cap. I replaced that, and the plugs and wires while I was at it. Idles good now, but the CEL is still on and still throwing code 28. One thing that is puzzling is that when I clear the code, either by pulling the EFI fuse or the battery, once i start the truck the CEL comes on immidietly. It doesn't allow the truck to run at all before the CEL is illuminated. Does this point to a burnt ECM? It has the later model ECM ending in 11 (I think only the 93's had the earlier version but I'm not sure) . I don't have access to another 94 ECM to plug and check that off the list but I don't know what else to try.
