diff --git a/clang/include/clang/Frontend/FrontendActions.h b/clang/include/clang/Frontend/FrontendActions.h
--- a/clang/include/clang/Frontend/FrontendActions.h
+++ b/clang/include/clang/Frontend/FrontendActions.h
@@ -34,6 +34,17 @@
   bool usesPreprocessorOnly() const override { return false; }
 };
 
+/// Preprocessor-based frontend action that also loads PCH files.
+class ReadPCHAndPreprocessAction : public FrontendAction {
+  void ExecuteAction() override;
+
+  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
+                                                 StringRef InFile) override;
+
+public:
+  bool usesPreprocessorOnly() const override { return false; }
+};
+
 class DumpCompilerOptionsAction : public FrontendAction {
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                  StringRef InFile) override {
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -62,6 +62,27 @@
 void InitOnlyAction::ExecuteAction() {
 }
 
+// Basically PreprocessOnlyAction::ExecuteAction.
+void ReadPCHAndPreprocessAction::ExecuteAction() {
+  Preprocessor &PP = getCompilerInstance().getPreprocessor();
+
+  // Ignore unknown pragmas.
+  PP.IgnorePragmas();
+
+  Token Tok;
+  // Start parsing the specified input file.
+  PP.EnterMainSourceFile();
+  do {
+    PP.Lex(Tok);
+  } while (Tok.isNot(tok::eof));
+}
+
+std::unique_ptr<ASTConsumer>
+ReadPCHAndPreprocessAction::CreateASTConsumer(CompilerInstance &CI,
+                                              StringRef InFile) {
+  return std::make_unique<ASTConsumer>();
+}
+
 //===----------------------------------------------------------------------===//
 // AST Consumer Actions
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -73,6 +73,8 @@
     if (!Compiler.hasDiagnostics())
       return false;
 
+    Compiler.getPreprocessorOpts().AllowPCHWithDifferentModulesCachePath = true;
+
     // Use the dependency scanning optimized file system if we can.
     if (DepFS) {
       const CompilerInvocation &CI = Compiler.getInvocation();
@@ -133,7 +135,7 @@
     // the impact of strict context hashing.
     Compiler.getHeaderSearchOpts().ModulesStrictContextHash = true;
 
-    auto Action = std::make_unique<PreprocessOnlyAction>();
+    auto Action = std::make_unique<ReadPCHAndPreprocessAction>();
     const bool Result = Compiler.ExecuteAction(*Action);
     if (!DepFS)
       FileMgr->clearStatCache();
diff --git a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
--- a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
+++ b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
@@ -156,6 +156,9 @@
   MDC.MainFile = std::string(
       Instance.getSourceManager().getFileEntryForID(MainFileID)->getName());
 
+  if (!Instance.getPreprocessorOpts().ImplicitPCHInclude.empty())
+    MDC.FileDeps.push_back(Instance.getPreprocessorOpts().ImplicitPCHInclude);
+
   for (const Module *M : DirectModularDeps)
     handleTopLevelModule(M);
 
diff --git a/clang/test/ClangScanDeps/modules-pch.c b/clang/test/ClangScanDeps/modules-pch.c
--- a/clang/test/ClangScanDeps/modules-pch.c
+++ b/clang/test/ClangScanDeps/modules-pch.c
@@ -9,5 +9,52 @@
 // Scan dependencies of the TU:
 //
 // RUN: sed "s|DIR|%/t|g" %S/Inputs/modules-pch/cdb_tu.json > %t/cdb.json
+// RUN: echo -%t > %t/result_tu.json
+// FIXME: Make this work with '-mode preprocess-minimized-sources'.
 // RUN: clang-scan-deps -compilation-database %t/cdb.json -format experimental-full \
-// RUN:   -generate-modules-path-args -module-files-dir %t/build
+// RUN:   -generate-modules-path-args -module-files-dir %t/build -mode preprocess >> %t/result_tu.json
+// RUN: cat %t/result_tu.json | sed 's:\\\\\?:/:g' | FileCheck %s -check-prefix=CHECK-TU
+//
+// CHECK-TU:      -[[PREFIX:.*]]
+// CHECK-TU-NEXT: {
+// CHECK-TU-NEXT:   "modules": [
+// CHECK-TU-NEXT:     {
+// CHECK-TU-NEXT:       "clang-module-deps": [],
+// CHECK-TU-NEXT:       "clang-modulemap-file": "[[PREFIX]]/module.modulemap",
+// CHECK-TU-NEXT:       "command-line": [
+// CHECK-TU-NEXT:         "-cc1",
+// CHECK-TU:              "-emit-module",
+// CHECK-TU:              "-fmodule-name=ModTU",
+// CHECK-TU:              "-fno-implicit-modules",
+// CHECK-TU:            ],
+// CHECK-TU-NEXT:       "context-hash": "[[HASH_MOD_TU:.*]]",
+// CHECK-TU-NEXT:       "file-deps": [
+// CHECK-TU-NEXT:         "[[PREFIX]]/mod_tu.h",
+// CHECK-TU-NEXT:         "[[PREFIX]]/module.modulemap"
+// CHECK-TU-NEXT:       ],
+// CHECK-TU-NEXT:       "name": "ModTU"
+// CHECK-TU-NEXT:     }
+// CHECK-TU-NEXT:   ],
+// CHECK-TU-NEXT:   "translation-units": [
+// CHECK-TU-NEXT:     {
+// CHECK-TU-NEXT:       "clang-context-hash": "[[HASH_TU:.*]]",
+// CHECK-TU-NEXT:       "clang-module-deps": [
+// CHECK-TU-NEXT:         {
+// CHECK-TU-NEXT:           "context-hash": "[[HASH_MOD_TU]]",
+// CHECK-TU-NEXT:           "module-name": "ModTU"
+// CHECK-TU-NEXT:         }
+// CHECK-TU-NEXT:       ],
+// CHECK-TU-NEXT:       "command-line": [
+// CHECK-TU-NEXT:         "-fno-implicit-modules",
+// CHECK-TU-NEXT:         "-fno-implicit-module-maps",
+// CHECK-TU-NEXT:         "-fmodule-file=[[PREFIX]]/build/[[HASH_MOD_TU]]/ModTU-{{.*}}.pcm",
+// CHECK-TU-NEXT:         "-fmodule-map-file=[[PREFIX]]/module.modulemap"
+// CHECK-TU-NEXT:       ],
+// CHECK-TU-NEXT:       "file-deps": [
+// CHECK-TU-NEXT:         "[[PREFIX]]/tu.c",
+// CHECK-TU-NEXT:         "[[PREFIX]]/pch.h.gch"
+// CHECK-TU-NEXT:       ],
+// CHECK-TU-NEXT:       "input-file": "[[PREFIX]]/tu.c"
+// CHECK-TU-NEXT:     }
+// CHECK-TU-NEXT:   ]
+// CHECK-TU-NEXT: }