ODB1 error 21 can't be cleared

Hi,

I'm running an imported 2001 Japanese Hiace Super Custom 2.4l petrol (2RZ-E engine). This doesn't have a OBD2 port - only the Toyota ODB1 / DCL1 port. The engine management light is NOT on but I connected the TE1 and E1 to get any flash codes. I got '21' - which I believe is oxygen sensor. I've done some reading and I came across something that said the computer will store a 21 error without putting the engine management light on - but will light it if it receives a second 21 on a subsequent drive.

I know the battery was replaced a month ago - so I assume the error was picked up since then. I thought it's reset it and see if it reoccurs. I've tried both disconnecting the EFI fuse for 30+ secs and also the vehicle's battery - but the error reoccurs immediately - even before starting the engine. I can't get rid of 21 flashing up on the dash when running diagnostics.

Could this mean the oxygen sensor is kaput or it's connection is effectively cut? But wouldn't this eventually bring up the engine light on the dash? I'm assuming 21 is the oxygen sensor but could the code mean something different on this vehicle?

Any thoughts welcome. Thanks

Good Afternoon Goose.

I thought code 21 was an open circuit on the O2 Sensor Heater. Failure would pop that light every time you power up the ECU.

From me book:
Code 21 Oxygen Sensor Heater Signal
*Open or short circuit in oxygen sensor heater signal(HT)*
​
Possible causes:
Oxygen sensor heater circuit
Oxygen sensor heater
ECU

Very likely your O2 sensor has failed Sir.

Good Luck and God Bless.
-Bryan

Thanks - the new sensor should be here for the weekend. I found more details in the 2rz-e supplemental manual:

For the diagnostics:

21: engine warning light for normal model / test mode: OFF / ON *1

*1: ”ON” displayed in the diagnosis mode column indicates that the check engine warning light is lighted
up when a malfunction is detected. ”OFF” indicates that the ”CHECK ENGINE” does not light up during mal-
function diagnosis, even if a malfunction is detected. ”N.A.” indicates that the item is not included in malfunc-
tion diagnosis.



So for the later petrol engines (2RZ-E), it says you only find out if the oxygen sensor is broken if you test for it! Unless this is referring to the '2 trip detection logic' where it needs two consecutive detections to set the engine light.


For info, test mode uses different pins in the diagnostic port:

DIAGNOSIS INSPECTION (Test Mode)
HINT:
Compared to the normal mode, the test mode has an increased sensing ability to detect malfunctions.
The same diagnostic items which are detected in the normal mode can also be detected in the test mode.
(a) Diagnostic Trouble Code Check
(1) Initial conditions.
Battery positive voltage 11 V or more.
Throttle valve fully closed.
Air conditioning switched OFF.
Check Connector
Turn ignition switch OFF.
Using SST, connect terminals TE2 and E1 of check connector.

Good stuff Goose.

A new sensor fixed it. One thing with working on a freshly imported van to the UK, no rusty nuts and bolts to worry about on the underside. If anyone else is doing this on a petrol van, the Denso (Toyota OEM) sensor is a DOX-0217

I had a guy hook up his laptop, J2534 adaptor and Techstream software. Wow! the stuff he could see... better than shorting a couple if pins and counting flashes. He said it didn't cost much.

That's really interesting. Just wondering what socket you have on your Hiace - and what sort of adaptor he used?