The Jeep, Dodge, or Chrysler cranks like it wants to start, then never fires. The security light on the dash is flashing or stays on. You try a second key and get the same result. That pattern is a SKIM no-start more often than a dead fuel pump.<\/p>\n
SKIM is Chrysler’s Sentry Key Immobilizer. Later vehicles moved the same job into SKREEM, then WIN. The idea stayed the same. If the key is not recognized, the PCM is told to withhold fuel and spark. The engine can crank all day and still never run.<\/p>\n
This blog covers how a SKIM no-start works, how to tell a bad key or antenna ring from a PCM that is no longer paired, and what has to be programmed before the vehicle starts again.<\/p>\n
A SKIM no-start means the immobilizer did not approve the key, so the PCM will not enable the engine. You will usually see a flashing security lamp, a crank with no start, and no injector pulse even though the starter is strong. The failed part may be the key, the antenna ring around the ignition, the SKIM or SKREEM module, or the PCM itself.<\/p>\n
This is a Chrysler-family problem. It shows up on Jeep<\/a>, Dodge<\/a>, and Chrysler<\/a> vehicles that use Sentry Key. It is not the same as a generic no-start from a dead crank sensor. If you just installed a used computer, read used ECU compatibility<\/a> before you chase sensors.<\/p>\n Watch the security light first. Then decide whether the key, the ring, the immobilizer module, or the PCM is the break.<\/p>\n SKIM keys have a transponder chip. A copied metal key with no chip, a key from another vehicle, or a chip that died will not be approved. After a battery disconnect, some vehicles also need a moment to relearn a valid key. They will not accept a blank one.<\/p>\n Try every original key. If one key starts the vehicle and the other does not, program or replace the failed key. Do not replace the PCM to fix a single dead transponder.<\/p>\n The antenna ring sits around the ignition lock cylinder and reads the chip in the key. When the ring fails, even a good key looks like a stranger. The security light flashes, and the engine cranks without starting.<\/p>\n This is a common miss because the key looks fine and the PCM still communicates. A shop can test the ring and the SKIM module together. Replacing the ring and programming the keys is a lot cheaper than a computer swap.<\/p>\n The immobilizer module stores the key list and talks to the PCM. Water in the column, a bad solder joint, or a failed SKREEM in the dash can drop that conversation. The PCM then defaults to no-run.<\/p>\n Scan for immobilizer codes and check communication with the SKIM, SKREEM, or WIN module. A silent security module is not the same diagnosis as a silent PCM. If you recently tried a reset, how to reset a Jeep ECU<\/a> will not pair new keys by itself.<\/p>\n The PCM has to share a secret with SKIM. A used, rebuilt, or replacement PCM that was never paired will crank and not start, even with the original keys and a healthy antenna ring. Brand-new keys will not fix a module that does not belong to that immobilizer yet.<\/p>\n This is why a PCM replacement on these vehicles has to include SKIM or SKREEM programming. The hardware can be correct and the engine will still refuse to run until that handshake is written. Owners of a Wrangler<\/a> or Grand Cherokee<\/a> hit this any time the computer is swapped without security pairing.<\/p>\n The security light and a second original key do most of the sorting.<\/p>\nCommon Causes of a SKIM No-Start<\/h2>\n
1. An Unprogrammed or Failed Key<\/h3>\n
2. A Failed Antenna Ring<\/h3>\n
3. A Failed SKIM or SKREEM Module<\/h3>\n
4. A PCM That Is Not Synced<\/h3>\n
How to Tell SKIM Causes Apart<\/h2>\n