error code 21 engine will run but wont idle

[Trey]

I have a 06/94 FZJ80R with 1FZ-FE engine 5 speed manual with 440,000 Km. The problem i am have is I can get it to start with throttle and run with throttle but it will not idle at all. I have pulled the codes and got an error code 21 (oxygen sensor). Does anyone know specifically what this code means (i noticed other oxygen sensor codes in the list) and also if the oxygen sensor could be causing this much trouble. The problem started a couple of months ago and gradually got worse. Any information would be greatly appreciated.

Cheers
Ashley

 

[CaptainKirk]

First suggestion - buy a Field Service Manual (FSM). Second - buy a meter and prepare to start testing. Did you get a CEL? If it is not disconnected, you most likely did. If there is a greater than 15% value between the front and rear sensor, the system yells foul. My suggestion is to do what I am about to (94 with 238,000 miles) - replace both O2 sensors.

 

[Trey]

Thanks for the reply. i have a FSM and meter will test tonight.
just priced the 02 sensor.... 340.00 AUD each

I also called the local toyota workshop and asked about the code, they said it was a "vacuum circuit malfunction" and to check the hoses on the MAP sensor.
I will up date with my test results asap.

Cheers
Ashley

 

[Trey]

Update... finally got to get back into the Cruiser (picked a up and worked on a Rolux with 5" suspention n 2" body lift 35" tyres for a mate) Found a massive crack in the intake hose, I attacked it with duct tape and will replace it tomorrow. She will idle for me now but very low (400-500rpm)
I spoke to another Toyota workshop, they are saying the code is for a 'vacuum hose malfunction' but the OBDI list on here state its the O2 sensor. I have looked for an OBDII code list but i cant find one. Thought maybe they were giving me the OBDII code. Any thoughts on the conflicting codes?? I will reset the codes tomorrow and check 'em when i get to work.

Cheers
Ash W.

 

[Atticus]

Your vehicle will run with a bad O2 sensor, just not at optimal level. If I were you, I would pull the code yourself and check it against an OBD I list (your rig is probably OBD I; in the States, we didn't get OBDII until sometime in the latter part of the 95 model run). Fixing the crack in the tube is likely going to fix the problem, but a Code 21 is an O2 sensor code: Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

If you have no other codes, pull the EFI fuse for 30 seconds or so to reset the ECU, and then restart. You will idle erratically for the first few start cycles, but after a while (iirc 20 starts or so), the ECU will recalibrate and you will be fine.

 

[CJF]

If there is a greater than 15% value between the front and rear sensor, the system yells foul. My suggestion is to do what I am about to (94 with 238,000 miles) - replace both O2 sensors.

If you have a US spec. 94, you most likely have parallel sensors before the cat's, not one before and one after (as with 95-97 OBDII's).

 

[HarleyHetz]

Good info, thanks for sharing!!

 

[HarleyHetz]

I have a pretty bad crack in mine too. And in fact, have the exact same symptoms, and the exact same code. I've attached a pic (at least I "hope" I did it right) that shows a vacuum line on the EGR valve that I was able to disconnect. Once disconnected, my truck would idle and run, albeit not quite normally, but it was a ton better than with it on. I'm getting a new hose tomorrow, I'll post back on how that does.

 

[Valden]

I’m writing this post in 2019 ... . My 1993 80 series with 1FZ-FE engine has been idling low for years. I’ve been using the hand throttle to keep the idle at a bit less than 800. I followed the instructions in the Engine Repair Manual and checked that the Idle Speed Control (ISC) valve was working. It is. The ECU diagnosis reported a code 21, indicating that the oxygen sensor was faulty. Testing with an ohm meter indicates that it is indeed open circuit and not working. Before replacing the sensor I performed an ECU reset and code clear by removing the 15 amp EFI fuse for a few minutes, with ignition off. Result - the engine is now idling correctly, at the first start, with no need for hand throttle intervention. Bewdy! Of course I’ll look into replacing the oxygen sensor, but at least my 80 series is idling properly, for the moment. I’ll report any further results of interest.

Edit: I’ve completed a test drive. Engine running and idle is good. Very smooth. The diagnosis system, via the flashing check engine light, is still showing code 21 for a faulty oxygen sensor, which seems fair given that I haven’t fixed it yet. I will monitor the situation. For the moment I’m happy, though I’m wishing I’d pulled that EFI fuse long ago.

 

[Lochie29]

I’m writing this post in 2019 ... . My 1993 80 series with 1FZ-FE engine has been idling low for years. I’ve been using the hand throttle to keep the idle at a bit less than 800. I followed the instructions in the Engine Repair Manual and checked that the Idle Speed Control (ISC) valve was working. It is. The ECU diagnosis reported a code 21, indicating that the oxygen sensor was faulty. Testing with an ohm meter indicates that it is indeed open circuit and not working. Before replacing the sensor I performed an ECU reset and code clear by removing the 15 amp EFI fuse for a few minutes, with ignition off. Result - the engine is now idling correctly, at the first start, with no need for hand throttle intervention. Bewdy! Of course I’ll look into replacing the oxygen sensor, but at least my 80 series is idling properly, for the moment. I’ll report any further results of interest.

Edit: I’ve completed a test drive. Engine running and idle is good. Very smooth. The diagnosis system, via the flashing check engine light, is still showing code 21 for a faulty oxygen sensor, which seems fair given that I haven’t fixed it yet. I will monitor the situation. For the moment I’m happy, though I’m wishing I’d pulled that EFI fuse long ago.

hey mate i have the same year and model car and it idles at 200 then cuts out i did the diagnosis and it came up with codes 21 and 24 which are the o2 sensor i have brought a new o2 sensor but it does the same thing idles at 200 then cuts out would anyone know what else it could be