It's the Fuel Air Ratio Sensor (which is an improved oxygen sensor, but expensive). After replacing the sensor (Denso 234-9024), the check engine light stays off. Case closed.
Harry (97 Camry LE 4-Cyl)
The following are the original messages:
=============================================== Got the check engine light two days ago. Went to Autozone and borrowed the scan tool yesterday. Got 5 codes as follows.
P0125 - Insufficient Coolant Temperature for Closed Loop Fuel control. P1135 - Air-Fuel Sensor Heater Circuit Response. P0171 - System too Lean. (Bank 1) P1130 - Air-Fuel Sensor Circuit Range/Performance. P1135 (Repeat)
Deleted the codes, but check engine light came back on after about 10 minutes of driving. Reset the check engine light this morning (by pulling EFI fuse for 1 minute). But again, it came back on after 10 minutes of driving. Any suggestion where I should start looking at? Thanks in advance. (Searched the net, some say "fuel air ratio sensor", others say "O2 sensor", "coolant temp sensor", etc.)
Car is a 97 Camry LE (4-Cyl), about 78K miles.
Harry (97 Camry LE 4-Cyl)
=============================================== After a few days of observation (by carrying a OBDII scan tool on my car and retrieve/reset the error codes once the check engine light comes up), here is a summary.
(1) Normally there are multiple error codes but sometimes there is only one. Example:
5/26 AM - p0125, p1130, p1135 5/26 PM - p0125, p0171, p1135 5/27 AM - p0125, p0171, p1130, p1133, p1135 5/27 PM - p0171, p0171, p1135 (p0171 comes up twice) 5/31 AM - p0125 (single error code) 6/1 PM - p1135, p0171, p1135 (p1135 comes up twice) etc (2) The Check Engine Light (CEL) normally comes up after about 10 minutes of driving, from a cold engine. There are couple of times that right after I got the CEL, reset it, then kept driving, the CEL never came up again, as long as the engine is hot. (3) The engine temperature looks normal. It may be a little bit lower then before, or it could be my imagination. The time for the engine to reach the normal temperature is about the same too.Base on the above observation, does it ring a bell to anyone?
Harry (97 Camry LE 4-Cyl, 78K miles)