1991 GMC C/K 1500 Problems: 2 Issues Every Owner Should Know
1991 model year · 0+ owner reports · Updated April 2026
According to Au7o's analysis of 0+ owner reports, the 1991 GMC C/K 1500 has 2 documented known issues. No issues are rated critical, indicating generally reliable ownership. Across all issues, repair costs range from $30 to $600. DIY maintenance guides at au7o.io.
All 2 Known Issues
On the 1988-1998 GMC C/K 1500, same oil pressure sensor issue as Chevrolet C/K 1500. The sending unit fails, giving false zero or erratic oil pressure readings. Oil can leak through the electrical connector. Aftermarket sensors have shorter service life. Always verify actual oil pressure with a mechanical gauge before condemning the engine.
Common Symptoms
- Oil pressure gauge reading zero at idle
- Oil pressure warning light flickering
- Oil leak from sensor area
- Erratic oil pressure readings
How to Fix
First, confirm the engine’s true oil pressure with a mechanical test gauge installed at the sender port; if pressure is within spec, the oil pressure sending unit is the likely fault rather than an internal engine problem. Inspect for oil wicking through the sender body or connector, then replace the sender with a quality ACDelco/GM unit and repair the pigtail if it is oil-soaked or brittle; on these trucks the sender is typically near the distributor/rear of the intake manifold on many V8s. Clear any leaked oil from the connector, verify stable gauge operation and no warning light flicker after replacement, and recheck for leaks. Typical cost is about $25-$60 for the sender, $20-$50 for a connector if needed, and roughly 0.5-1.0 hour labor, bringing most shop repairs to about $100-$250.
What Owners Are Using
Parts and tips from 0+ owners who fixed this issue
- UpgradeBluetooth OBD-II scanner for reading engine codes and monitoring live data (BlueDriver Bluetooth OBD2 Diagnostic Scan Tool)
- UpgradeQuality synthetic oil and filter combo for engine maintenance (Mobil 1 Full Synthetic Oil and Filter Bundle)