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Car Forum / Toyota / Toyota Cars / January 2009Check Engine Light help request - 2003 RAV4
This is my first experience ever with a Check Engine Light. Since my car (2003 RAV4, 4 cyl.) is almost 6 years old, I figured it may not be my last, so I picked up an OBD2 reader (Innova 3030, $58 at Wal-Mart). My first reading showed no codes, but indicated that four of the Monitor tests were not complete. After driving several miles in the attempt to complete those Monitor tests (two of the four never did complete--the Catalyst Monitor and the Oxygen Sensor Heater Monitor) the reader finally did show a single diagnostic code, P1155. The manual says that is a "Air/Fuel Heater Circuit Malfunction." Is it necessary to complete those two Monitor tests? Might additional codes be displayed? And if so, how do I have to drive to complete them? And what might be the problem, how to repair/replace, etc.? I'd sure appreciate any help! --John Wells > This is my first experience ever with a Check Engine Light. Since my > car (2003 RAV4, 4 cyl.) is almost 6 years old, I figured it may not be [quoted text clipped - 19 lines] > > --John Wells Typically it's the O2 sensor, but I've never heard of the "Air/Fuel Heater Circuit Malfunction", which might refer to the Air mass sensor. O2 sensors usually run about $80, for an NTK OE replacement. There are usually two O2 sensors on the later model Toyotas. One before the CAT and one after the CAT. Here is a link for an example: http://www.ngksparkplugs.com/products/oxygen_sensors/index.asp?mode=nml >> This is my first experience ever with a Check Engine Light. Since my >> car (2003 RAV4, 4 cyl.) is almost 6 years old, I figured it may not be [quoted text clipped - 25 lines] >sensors on the later model Toyotas. One before the CAT and one after the >CAT. From what I've been able to find out, Toyota used a (relatively inexpensive) O2 sensor prior to 1991, but went to the more costly A/F sensor after that (upstream from the CAT--I think the downstream one may still be an O2). >Here is a link for an example: >http://www.ngksparkplugs.com/products/oxygen_sensors/index.asp?mode=nml That was educational! Thanks for your help! --John W. Wells > From what I've been able to find out, Toyota used a (relatively > inexpensive) O2 sensor prior to 1991, but went to the more costly A/F > sensor after that (upstream from the CAT--I think the downstream one > may still be an O2). The secondary sensor (after the cat) is _always_ an O2 sensor. Toyota began using A/F sensors in 1997, starting with the 1997 CA-market 4-cylinder Camry. By '02, only 4-banger Toyotas and a couple of V6's still used O2 sensors for the primary. A/F sensors may be across-the-board now for the primary, but I'm not sure.  SignatureTegger >> From what I've been able to find out, Toyota used a (relatively >> inexpensive) O2 sensor prior to 1991, but went to the more costly A/F [quoted text clipped - 8 lines] > >A/F sensors may be across-the-board now for the primary, but I'm not sure. And to add to my confusion, when I picked up the car yesterday, the repair shop's receipt listed them as "O2 sensors." And both of the old parts are identical (Denso, Toyota OEM). The counter man said that A/F, O2, whatever--they're all called O2 sensors now! Wunnerful! Thanks for your reply! --John W. Wells > The counter man said > that A/F, O2, whatever--they're all called O2 sensors now! Maybe to him. But that's /very/ sloppy terminology. He probably just said that to cover up his own ignorance. A/F sensors and O2 sensors operate in vastly different manners and are NOT interchangeable. SignatureTegger > This is my first experience ever with a Check Engine Light. Since my > car (2003 RAV4, 4 cyl.) is almost 6 years old, I figured it may not be [quoted text clipped - 19 lines] > > --John Wells John, If you clear diagnostic trouble codes (DTC) from the memory, then the vehicle will indicate "not ready" until the readiness monitor drive cycle is complete. It is possible for additional DTC's to come up when the drive cycles is complete. The factory repair manual will have information on how to complete the readiness drive cycle, but basically, it is start with the engine cold, let the coolant temperature reach normal, then drive at 30 MPH for a couple of miles, then drive at 50 MPH for a few miles. Basically, you want every sensor in the car, including speed and temperature sensors, to have a chance to send a good signal to the computer at least twice. As far as the Air/fuel Sensor Heater circuit malfunction, the A/F sensor is basically like an oxygen sensor, except that CA emissions vehicles us an air/fuel sensor and federal emissions vehicles use oxygen sensors. These sensors have to be pretty hot to operate properly, they have an electric heater to heat them up more quickly. If the heater doesn't work on 2 consecutive trips, then you will get a check engine light. I'm not sure of the exact location of the A/F sensor in your car, but it is probably in the exhaust manifold. Check the heater wire for an open circuit, and if you have an open circuit or short to ground, replace the A/F sensor. SignatureRay O (correct punctuation to reply) >> This is my first experience ever with a Check Engine Light. Since my >> car (2003 RAV4, 4 cyl.) is almost 6 years old, I figured it may not be [quoted text clipped - 33 lines] >want every sensor in the car, including speed and temperature sensors, to >have a chance to send a good signal to the computer at least twice. I tried (and tried!) that, but to no avail, though I did manage to clear a couple more. >As far as the Air/fuel Sensor Heater circuit malfunction, the A/F sensor is >basically like an oxygen sensor, except that CA emissions vehicles us an >air/fuel sensor and federal emissions vehicles use oxygen sensors. These >sensors have to be pretty hot to operate properly, they have an electric >heater to heat them up more quickly. If the heater doesn't work on 2 >consecutive trips, then you will get a check engine light. My car was was purchased in Oregon, but I see that Toyota, since 1991, uses A/F sensor(s) rather than the O2 variety. >I'm not sure of the exact location of the A/F sensor in your car, but it is >probably in the exhaust manifold. Check the heater wire for an open >circuit, and if you have an open circuit or short to ground, replace the A/F >sensor. Yes, I found them OK. But then what to do... This is my wife's car, and thus speed is of the essence! So we dropped it off at a repair shop this morning. $590 to replace both sensors <shudder>. But I've read that 100,000 miles is a pretty good life for these things (we're at 83K), so we're doin' our bit to rehab the economy--at least the auto repair part, if not the geezers-on-fixed-income part! Thanks for your help! --John W. Wells |
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