Big Hurt Posted June 30, 2009 Share Posted June 30, 2009 My 2000 LX 470's AHC off light is blinking and the truck is in the low position. The manual say it will automatically go into the normal ride height but mine will not. Where do I start to troubleshoot the AHC problem. My accumulators are fine. What else??? Quote Link to comment Share on other sites More sharing options...
lx470tuner Posted July 1, 2009 Share Posted July 1, 2009 It sounds like your ahc pump is having some issues. Keep in mind that your pump motor can still run (so the fault can go undetected) but the pump can fail to move the fluids. Number of reasons cause this issue, inlcuding air creap past the shaft seal into the pump, damages pressure valve and nitrogen depletion (that last one is not likely since you mentioned that your accumulators are fine). The best way to diagnose if this is true is to manually operate the ahc pump and see if fluids are moving. If this is the case, the best solution is replace the pump sub assembly. Don't forget to bleed the system after the replacement :D -Dave Quote Link to comment Share on other sites More sharing options...
Big Hurt Posted July 3, 2009 Author Share Posted July 3, 2009 It sounds like your ahc pump is having some issues. Keep in mind that your pump motor can still run (so the fault can go undetected) but the pump can fail to move the fluids. Number of reasons cause this issue, inlcuding air creap past the shaft seal into the pump, damages pressure valve and nitrogen depletion (that last one is not likely since you mentioned that your accumulators are fine). The best way to diagnose if this is true is to manually operate the ahc pump and see if fluids are moving. If this is the case, the best solution is replace the pump sub assembly. Don't forget to bleed the system after the replacement :D -Dave Thanks Dave, If the accums are defective will that prevent the pump from working and give me that indication? I have replaced them before with the B & B accums and I have not had much luck I think it's time for me to purchase them from Lexus. And operating the pump manually is that difficult to do and what type of equipment would I need? Quote Link to comment Share on other sites More sharing options...
mann777 Posted July 21, 2009 Share Posted July 21, 2009 Big Hurt, it is nothing to do with the AHC pump but some of the 02/03 models exhibit a flashing AHC "OFF" light with the DTC code 1743 in the AHC ECU memory. All it needs is a change to the relay unit performance. Old Part Number - 90987-02004 Current Part Number - 89278-60010 - Relay Height Control. For location and replacement you have to refer to the TIS manual AHC Relay location. There was a TSB issued, maybe if somebody has can publish it for you. Quote Link to comment Share on other sites More sharing options...
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