Onboard Diagnostics

The Astro/Safari vans are available with two different onboard diagnostic systems.

1988-1995 model years use GM's proprietary  ALDL (Assembly Line Data Link).
Diagnostic Codes / Trouble Codes can be retrieved using a specialized diagnostic code readers or by jumping the Flash Code Request terminals to ground.
12 pin
A = Ground
B = ECM "Service Engine Soon" Flash Code Request
K = SIR "AIR BAG" Flash Code Request
M = 8192 Baud Data

1996-2005 model years use the USA automotive industry standard OBD-II (Onboard Diagnostics II).
Diagnostic Codes / Trouble Codes can only be retrieved using a specialized diagnostic code readers that are compatible with GM's SAE J1850 VPW
16 pin

Panlong OBD-II Bluetooth adapter
Two models available Android and iOS/Android. (Does iOS really need a special more expensive adapter?)
Android Only
https://www.amazon.com/Panlong-Bluetooth-Diagnostic-Scanner-Android/dp/B00PJPHEBO?th=1
iOS / Android
https://www.amazon.com/Panlong-Scanner-Bluetooth-Android-Diagnostic/dp/B0C1GDJ9ZJ?ref_=ast_sto_dp&th=1

OBD-II Android apps
Torque Lite: https://play.google.com/store/apps/details?id=org.prowl.torquefree
Torque Pro: https://play.google.com/store/apps/details?id=org.prowl.torque