DTC P1500: Engine Starter Signal Circuit Malfunction
WARNING: This page is about a different car, the 1999 Suzuki Vitara. However, it is still accessible from the selected car via links, so may be relevant.
Remove PCM cover. Using DVOM, measure voltage between ground and (backprobe) PCM harness connector terminal C51-3-18. If voltage is 6-12 volts while cranking and 0-1 volt after starting engine, check for poor PCM harness connections or intermittent problem. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If connections are okay and no intermittent problems were found, replace PCM and retest system. If voltage is not a specified, repair open in Black/Yellow wire between starter and PCM.