SC300 odometer flashes
07-31-22, 05:44 PM
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SC300 odometer flashes
i recently replaced the ac compressor on my girlfriends sc300. all went well, aside from forget to tighten the power steering line and spewing fluid for a bit. upon starting it to get the charging process going, the odometer starting flashing between trip 777777, odo 222222 and some other funky stuff. cel reads code 27, afr rich, which has been the case for awhile that’s nothing new. battery was removed and disconnected during install, all connectors are back and grounds are on. i’m stumped.
note- ecu was previously replaced with a 60k mile ecu from a recycler. new maf, rebuild distributor.
my question is, should i be looking at an ecu issue, a wiring harness issue, or a cluster issue? i know cluster issues are very common, but speedo and tach work as is so i’m leaning away from that. literally any insight would be great, i’ve searched everywhere and only found 1 thread on another forum that was left unanswered. thanks!
note- ecu was previously replaced with a 60k mile ecu from a recycler. new maf, rebuild distributor.
my question is, should i be looking at an ecu issue, a wiring harness issue, or a cluster issue? i know cluster issues are very common, but speedo and tach work as is so i’m leaning away from that. literally any insight would be great, i’ve searched everywhere and only found 1 thread on another forum that was left unanswered. thanks!
07-31-22, 10:52 PM
#2
Hello and welcome to CL!
I think this specific question is one that O.L.T. or Tanin Auto could answer. I don't think the odometer errors are directly ECU related but even if you got a 60k mile ECU not long ago you should still consider getting its capacitors changed out simply due to its age.
The odometer circuit and logic takes (I think) its data sources primarily from one or both of the front ABS wheel speed sensors and also from the transmission's VSS sensor (which is primarily there to provide a speedometer signal). That being said I am not sure myself if this points to some kind of fault within the instrument cluster itself.
The CEL code 27 points to the sub-oxygen sensor signal being off. This should be a four-wire heated O2 sensor located on your 2nd catalytic convertor under the main body of the car alongside the transmission. Is your car an original California Emission SC300 or 1996+ SC300? The connector for that O2 sensor is accessed by removing the center console and lifting up the carpet on the driver's side below the radio. You cannot get to it easily without removing the center console's top trim and the center console itself.
...
Before getting into replacing it however, if that low miles ECU has never had its capacitors replaced I would recommend sending it in to Tanin Auto Electronix or SIA in order to get it refreshed. A lot of strange phantom issues, CELs and poor running conditions have been reported with SC300's and SC400's over the years all having been due to their ECU capacitors going bad and requiring replacement service.
It's a pretty common thing to need to get done with most older electronics that use electrolytic capacitors.
The weirdness with the cluster may be its own issue that needs correcting. I don't know but the experts on that would.
I think this specific question is one that O.L.T. or Tanin Auto could answer. I don't think the odometer errors are directly ECU related but even if you got a 60k mile ECU not long ago you should still consider getting its capacitors changed out simply due to its age.
The odometer circuit and logic takes (I think) its data sources primarily from one or both of the front ABS wheel speed sensors and also from the transmission's VSS sensor (which is primarily there to provide a speedometer signal). That being said I am not sure myself if this points to some kind of fault within the instrument cluster itself.
The CEL code 27 points to the sub-oxygen sensor signal being off. This should be a four-wire heated O2 sensor located on your 2nd catalytic convertor under the main body of the car alongside the transmission. Is your car an original California Emission SC300 or 1996+ SC300? The connector for that O2 sensor is accessed by removing the center console and lifting up the carpet on the driver's side below the radio. You cannot get to it easily without removing the center console's top trim and the center console itself.
...
Before getting into replacing it however, if that low miles ECU has never had its capacitors replaced I would recommend sending it in to Tanin Auto Electronix or SIA in order to get it refreshed. A lot of strange phantom issues, CELs and poor running conditions have been reported with SC300's and SC400's over the years all having been due to their ECU capacitors going bad and requiring replacement service.
It's a pretty common thing to need to get done with most older electronics that use electrolytic capacitors.
The weirdness with the cluster may be its own issue that needs correcting. I don't know but the experts on that would.
Last edited by KahnBB6; 07-31-22 at 10:56 PM.
08-01-22, 08:08 AM
#3
2nd gear
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Join Date: Jul 2022
Location: Kansas
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Hello and welcome to CL!
I think this specific question is one that O.L.T. or Tanin Auto could answer. I don't think the odometer errors are directly ECU related but even if you got a 60k mile ECU not long ago you should still consider getting its capacitors changed out simply due to its age.
The odometer circuit and logic takes (I think) its data sources primarily from one or both of the front ABS wheel speed sensors and also from the transmission's VSS sensor (which is primarily there to provide a speedometer signal). That being said I am not sure myself if this points to some kind of fault within the instrument cluster itself.
The CEL code 27 points to the sub-oxygen sensor signal being off. This should be a four-wire heated O2 sensor located on your 2nd catalytic convertor under the main body of the car alongside the transmission. Is your car an original California Emission SC300 or 1996+ SC300? The connector for that O2 sensor is accessed by removing the center console and lifting up the carpet on the driver's side below the radio. You cannot get to it easily without removing the center console's top trim and the center console itself.
...
Before getting into replacing it however, if that low miles ECU has never had its capacitors replaced I would recommend sending it in to Tanin Auto Electronix or SIA in order to get it refreshed. A lot of strange phantom issues, CELs and poor running conditions have been reported with SC300's and SC400's over the years all having been due to their ECU capacitors going bad and requiring replacement service.
It's a pretty common thing to need to get done with most older electronics that use electrolytic capacitors.
The weirdness with the cluster may be its own issue that needs correcting. I don't know but the experts on that would.
I think this specific question is one that O.L.T. or Tanin Auto could answer. I don't think the odometer errors are directly ECU related but even if you got a 60k mile ECU not long ago you should still consider getting its capacitors changed out simply due to its age.
The odometer circuit and logic takes (I think) its data sources primarily from one or both of the front ABS wheel speed sensors and also from the transmission's VSS sensor (which is primarily there to provide a speedometer signal). That being said I am not sure myself if this points to some kind of fault within the instrument cluster itself.
The CEL code 27 points to the sub-oxygen sensor signal being off. This should be a four-wire heated O2 sensor located on your 2nd catalytic convertor under the main body of the car alongside the transmission. Is your car an original California Emission SC300 or 1996+ SC300? The connector for that O2 sensor is accessed by removing the center console and lifting up the carpet on the driver's side below the radio. You cannot get to it easily without removing the center console's top trim and the center console itself.
...
Before getting into replacing it however, if that low miles ECU has never had its capacitors replaced I would recommend sending it in to Tanin Auto Electronix or SIA in order to get it refreshed. A lot of strange phantom issues, CELs and poor running conditions have been reported with SC300's and SC400's over the years all having been due to their ECU capacitors going bad and requiring replacement service.
It's a pretty common thing to need to get done with most older electronics that use electrolytic capacitors.
The weirdness with the cluster may be its own issue that needs correcting. I don't know but the experts on that would.
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