[irogag]

If you are talented with soldering (or just decent at it) and electrical troubleshooting; please attempt the following "Irogag's Sure-fire Immob Recondition":

Alarm control unit: M535
Year: Mine is 2000 Boxster Non-S, Not sure how many others this applies to. A few for sure.
Model: 986 (possibly others)


Before Beginning) IF you have a system tester or diagnostic tool, it could be very useful to know what Code is displaying. For example, "Code 21 W Lead" will mean you should focus your skills near the Plug I, control module, Terminal # 23. If W Lead ''goes true" every time, and that it passed to the alarm control unit. This was the issue I found. It's very simple: if the signal is NOT there, then it's a problem outside the module elsewhere in the vehicle. If it's there, and it seems like the signal is present up to the module, then start to suspect the M535. The R1 relay in the photo attached was bad, and I just bought it for $0.75 and problem solved.

But without a diagnostic tool, I can take you through about 80% of alarm issues (with the control module) solved by this step-through:

1) E-1 Fuse OK?
2) F-5 Fuse OK?
3) Does the door lock button (central locking button) operate? Does system recognize both doors? Do both doors lock? Does rear lid get recognized? Does front interior lights come on when front compartment lid is open? The procedures assumes yes to all these. If none of this works, start there. The lids may not matter, but again it's best to get all these inputs correct to get a good 'lock' for alarm readiness.
3)Disconnect neg (-) Battery cable.
4)Remove seat
5)Unplug Plug I (blue) and Plug II (black) from the M535. Pull on each wire in the plug harness to verify they are tight. Check for anything obviously bent, burnt, broken or loose on all plug holes on plugs and all pins on module.
6) Remove M535 and remove plastic around it. Take the PCB to a workbench.
7)Use a clean toothbrush and denatured alcohol to clean top and bottom of PCB. Clean it really well.
8)Unsolder and replace the blue capacitor in the center.
8.1) Test fuse next to plug II (black PCB-mounted plug connector). Fuse OK?
9) Apply the necessary voltage to the necessary 2 pins on each relay, R1 to R7. Take your time and look up each part # on the web to know what voltage to apply. I used just a regular voltage power supply which let me vary the voltage as required.
10) As you apply voltage, check the contacts with an ohmmeter. A open should always be O.L. or >1 Meg-Ohm. A close should always be < 0.5 Ohms. Any readings besides these mean the relay is suspect. I applied it with a direct voltage right on solder side of the board. Alternately, you can use a magnetic to move the contacts but be warned this may not detect all issues using a magnet alone. It's best to test with actual voltage similar to what the car is putting out.
11) For 'double pole' relays check both poles and both contacts on each pole. Check the N.O. is open with no power. Check the N.O. closes with power. Check the N.C. is closed with no power. Check the N.C. is open with power. It sounds obvious, I know, but you really must carefully check each pin on those relays to prove they work. My issue was with a N.O. contact staying open, no matter what I did to the relay on R1.
12)If you've made it this far and found absolutely no issues, or even if you've fixed something, it's best to reinstall the module now to test it in the car. Reconnect (-) battery cable. Notice any changes ?
13) If no changes are noticed, please make sure you did step 8, and Step 9 thru 11 carefully. Double check all your work. I say this because we may destroy your M535 in the next steps so be advised. If you've made it this far your issue is likely not the module. I would send it in for repair, buy a new transponder, key, and M535 from the website guys, or start troubleshooting elsewhere in the car first. If you are still stuck and convinced it's the M535, and you have proof to back that up, please continue below:
14) We are going to 'reflow' all the solder on the board. I highly recommend looking up ''reflow a PCB in oven" on Google for how to do this. Alternately, what I did what cover the relays and capacitor with about 3 sheets of heavy duty aluminum foil. Then, I applied heat from a heat gun directly at the ICs and pcb components of the module.
15)When reflowing, always place a small 'mouse poop'sized stick of solder on the largest IC. This will turn into a ball when you know you are hot enough to melt all solder on board. Finally, it's crucial to keep the PCB level to keep from flowing solder away from IC pads.
16) Resolder or just put a lot of heat at the pins of the PCB-mounted plug connectors. Skip this step if you reflow in oven, as that pretty much covers all the solder on the whole PCB.
17) Wait patiently for at least 20 minutes to even move the board.
18) Reinstall module to test in the car.
19) Again, I am assuming you've already tried all the other clutch safety switch, ignition lock, and other various component troubleshooting. The M535 is pretty simple, so if it's not getting an obvious signal like K-Lead or W-Lead for real (which was not my case, it was getting those just not interpreting them via the module correctly) - then start your troubleshooting on much more simple terms such as checking resistances, checking that grounds are grounded, etc.
20) If you did not fix it by now I would pay the $600 or so for the full repair. But I would advise first to prove the issue is immobilizer based and not a much more simple issue with the key, the ignition switch, etc.

NOTE) None of these steps above address non-control modules, such as issues with your ignition lock, your transponder, your motion sensor/IR sensor, or any other parts of the car.