Help! Issue with PCM on an 01 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to   Members

ECUs and Tuning Discuss Engine Management, Tuning, & Programming

LinkBack Thread Tools Search this Thread
Old 05-19-2012, 01:22 PM   #1
Thread Starter
Join Date: Nov 2009
Location: New Mexico
Posts: 5
Total Cats: 0
Default Help! Issue with PCM on an 01

I am posting this hear because there appears to be so much expertise around PCMs and alterations that someone may be able to point me in the correct direction. I have a 2001 with a PCM which contains a flashed chip (stock motor). It has been acting erratic so I decided to put a stock PCM back into it. I have put two new PCMs into it with the same result They both trigger the Immobilizer light the moment the key is turned and will crank but not start (disables the ground circuit for the F/P relay, the coil circuit and a few others). My research indicates this early light means a key/ immobilizer mismatch as the CPM will not register the Key. BUT with both CPMs I swapped out the complete CPM, Immobilizer, Keys, and Starter Switch with Halo. When I try them on another vehicle they fire up perfectly (one was from a 2001 and the other a 2003).

This points to a problem with the Harness. I have the 2001 shop manual and the Miata immobilizer training manual and have run all the tests on the circuits they indicate with nothing out of spec AND when I put the Flashed PCM and related parts back the car fires right up?!.
Incredibly perplexing. There has to be another circuit unrelated to the immobilizer which is messing up the new CPM's but I cant imagine which. I have checked the ground circuits and they are okay. Does anyone have any idea what additional circuits related to the CPM that may be the culprit here?
hoochy coochy man is offline   Reply With Quote
Old 05-20-2012, 04:34 PM   #2
Thread Starter
Join Date: Nov 2009
Location: New Mexico
Posts: 5
Total Cats: 0

It appears my post has failed to generate much interest but I do have an update. A bit of dumb luck - I was rummaging through my heap of spare parts and I came across a complete intact engine harness for a 2001 I had forgotten about!! I think it covers most sensors with the exception of the FTP and I have a manual transmission. This harness does of course tie into the side harness' but that tie-in does not compromise the connections between the majority of sensors which are direct to PCM with in the harness. This still leaves some question around the Immobilizer of course but if needs be I can run a direct line from the immobilizer to the PCM! With some luck I may narrow the culprits today or maybe even resolve the problem.
hoochy coochy man is offline   Reply With Quote
Old 05-20-2012, 04:48 PM   #3
Supporting Vendor
iTrader: (10)
Reverant's Avatar
Join Date: Jun 2006
Location: Athens, Greece
Posts: 5,440
Total Cats: 198

If you have swapped the complete set (PCM, immobilizer module, keys, locks) each time and they dont start (whereas they were starting the previous time with the "chipped" PCM), then the sets swapped do not have matching PCMs/modules/keys.
Reverant is offline   Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
Raleigh: Fiberglass headlight scope, 1.6L ECU, AFM, Hardtop latches, more bigmackloud Miata parts for sale/trade 13 09-22-2017 01:34 PM
Bizarre connection issue? nick470 MEGAsquirt 1 09-30-2015 11:32 PM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 11:28 PM
Odd Steering issue interestedofold Suspension, Brakes, Drivetrain 5 09-29-2015 02:42 PM

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -4. The time now is 08:44 AM.