Tom Stacy

Remember to swap out the Memcal chip from your ECU into the "new" ECU. Use proper grounding when doing so. You may want to search this forum for "turbo boost" and see if there are any other threads on this topic to aid in your troubleshooting.

You need to attach the cable to a USB port on your laptop. Look at the picture below and you will see there is an interface cable that converts from serial (DB9) connector to USB. You can order this from SanJ on EBAY here: https://www.ebay.com/itm/175448207955?itmmeta=01J3AEQNWFN72M3EFY1CJQ94D4&hash=item28d9873253:g:u44AAOSwgVdfZjYW&itmprp=enc%3AAQAJAAAA8DoVo2cWm9pJ1hxrlUnksw00EvIvmZ94yE5I49lL9CFQSuOOXgi1f6MqJRGzbdrTSLt%2BkzXsS72dk%2BUhxrbg38BT2GWELAIvbTzPDRp2Lp5puAFOQ9AuPGCMf66pvwcmISSGEJYGsCtRBxTGmtugEtXzAf9hHmNVNj4T%2BxeZfFvexspRwcrYZBA7Tbly9qL7wkXWnARjUrUhIbqxuw6c2auo%2Bof2qGxIfWtskBcE0D4aO6cis%2BJJbkFhZMwlwuXUZK3hD%2BBLnCkIkLYCae7GPddtrGOdjPP1mcEL0KXLMtQ8GaijPaBMeP20vG5O30TisQ%3D%3D|tkp%3ABk9SR6je3s6aZA

Hi, Error code 42 denotes Ignition bypass circuit error. Mine was associated with a faulty(original) ECM unit which I replaced from a 1991 chevy beretta. Detail troubleshooting is available in the Lotus EMH service manual which I included for your discretion. Freescan is a useful diagnostic tool free to download, also included. You will need to reach out to SanJ to obtain the interface cable for ALDL to laptop interface. His email is <turboesprit@earthlink.net>. He also sells them on EBAY. ECU removal is shown here and also on Youtube. http://www.lotusespritworld.com/EGuides/EModifications/chip_install.html Lastly, I picked up a spare '91 chevy beretta ECU on EBAY, had SanJ program the EEPROM, then installed it into the circuit and plugged it in to validate functionality. Now I have a spare unit in the event that I need to replace the unit in the future. Good luck, Tom S. Section EMH - Electronic M.P.F.I. With Chargecooler - B082T0327Z.pdf freescan_210.zip

Probably not inexpensive as you say, but they are cheap enough and available on EBAY. I found one (#1228707) for under $25 and free shipping. Can't beat it, worth the investment for future insurance. TS

Tested EST circuitry, no opens or shorts. Ran Freescan, reviewed data, nothing out of the ordinary except IAC stuck at 170. Swapped IAC, ran freescan and found no longer stuck but error 42 still persists with rough idle and stall. Removed ECU, swapped out with spare unit and installed MemCal chip. Started car, idle immediately leveled out at 1350RPM, with no stalling. Faulty ECU was the issue for code 42. Will buy another spare on EBAY to keep on hand.

Has anyone experienced this error code on their Esprit? Symptom is after starting, idles high, drops to 1200-1400RPM, then sputters and eventually stalls. Did this to me while driving for 10 minutes or so. Read code as DTC-42 : Ignition bypass Circuit error. I thought about replacing the IAC and TPS since both could cause this condition, but error code tells me that it may be ECM related. Any thoughts from experience out there? Thanks. Tom S. '89 Lotus Esprit Turbo x180