auto-electrician's Oscilloscope (Cainscross GL5)

Ideally a 4-channel scope to borrow for a short time to help me pinpoint the source of a fault I'm seeing on my van - it must be either inside (££-ouch!) or outside (wiring/fuses/relays/connectors) the ECU
The wiring etc. all pass standard load/bench tests, but I may be missing a transient blip too short for them to pick up...