Magic Carp

I hate My Little Pony with a passion.

This explanation is based around single player car mods only, with only a couple exceptions.
 
 
TABLE OF CONTENTS
 
I. INTRODUCTION
II. ISSUES REGARDING REPLACING VEHICLES
III. ISSUES REGARDING ELS V7
IV. ADDENDUM 1 - MULTIPLAYER
V. ADDENDUM 2 - SAVING WHILST ON DUTY
 
 

Introduction

First, this guide will not cover the cause of every single SMPA60 error.  This error is far more complicated than we once thought (even LMS doesn't know everything about it).  As such, it is impossible to cover every cause and respective resolution.  This guide will not cover errors caused when LCPDFR 1.0 is installed, as we do not know what is happening there.
 
You will know when you experience an SMPA60 error because you will receive an error message like this:


image from gtaforums

The way the game is set up, whenever you save the game and there is a vehicle at a safe house, it writes more than just the name of the car to the save game file. It also seems to record the car components, extras, model and skin details, et cetera. No one, except for the developers of GTA, knows exactly how the game writes the data.
 
Issues with Replacing Vehicles
 
So let's get to the problem. Many players like to download modded cars and then use them in GTA IV. There is nothing wrong with this. Some LCPDFR users also like to download new police cars and use those as well. Naturally, many people also like to save vehicles at their safe house for future use. Unfortunately, this is the main source of the problem.

From here on I will use these two cars for an example: A Crown Vic (already in game) and a Dodge Charger (car you want to replace the Crown Vic with).

So lets say that someone has a Crown Victoria in their game. They eventually get bored of it, just like many people do, so they decide to replace it with a Dodge Charger instead. When they replace the Crown Victoria's .wtd and .wft files (the model and texture files) with those of the Dodge Charger, they overwrite the Crown Vic data files. This happens every time you import a car mod. However, now that the Crown Vic is replaced, upon loading the game GTA tries to take the data it saved from the last save game and then apply it to the Dodge Charger. This simply does not work. The game becomes scrambled, it has no idea what to load, where to put things, or what to do. It then faults, crashes to the desktop (also known as a CTD), and outputs an SMPA60 error code.

The best way to avoid this, naturally, is to never save cars at your safe house. But that is completely impractical. Thus, the next best thing to do is to ALWAYS check what you have saved before you replace a car. Another good practice is to SAVE the old car mod data (in my previous example, the Crown Victoria) in a backup folder before replacing it just in case the game faults and you need to re-import it. Should you have a car saved, and you wish to replace it, you MUST remove it from the safe house and THEN save the game. Failure to do so will cause your game to CTD when loading the game with replaced car data.
 
Issues Regarding ELS v7
 
It has been brought to my attention (thanks, DarthWound) that ELS v7 may cause an SMPA60 error.  This seems to be related to allowing AI vehicles to use ELS.  The best course of action is to disable AI ELS if this problem affects you, however you can also change the ClearRandAiExtras setting in the ELS config file.  This will stop ELS from removing the lights on AI vehicles that randomly stay on when the car first spawns (think ELS v6 and earlier). To disable AI ELS, change this line in the ini file: AI_ELS_SP = OFF
 
Addendum I

As Olanov stated a few comments down, it is also likely that one will get an SMPA60 error while in a multiplayer game, if players are using different vehicle mods. In this case the only thing for you to do is to completely remove your mods from the game before you play multiplayer. The best alternative is to have two vehicles.img. One for SP and one for MP.
 
Addendum II

Some say that saving your game while an officer will cause an SMPA60 as well. I have never seen this happen, but it does make sense. I will note that if the game starts to load and IMMEDIATELY CTD's with an SMPA60, meaning it crashes in the loading screen, you should try to remember if you saved as a cop. If you did, your savegame file is GONE for good. If, however, you can start to play the game and it crashes during play, then follow the above steps, since it is probably caused by cars.