diff --git a/src/main/javascript/update_code_display.js b/src/main/javascript/update_code_display.js
new file mode 100644
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--- /dev/null
+++ b/src/main/javascript/update_code_display.js
@@ -0,0 +1,265 @@
+// This is a stand alone node script to iterate through the modules
+// and update all code displays that do not match an allowed value.
+// (i.e., code displays that would not pass FHIR validation)
+// The script also attempts to standardize when the same code is used in
+// multiple modules, and to minimize the number of updates.
+// Any invalid/unknown codes will be printed to console.
+//
+// Note this does require the `sync-fetch` library to be installed first.
+// 
+// Example:
+//   npm install sync-fetch
+//   node update_code_display.js /path/to/synthea/src/main/resources/modules/
+//
+// Tested on node v20.3.1
+
+const fetch = require('sync-fetch')
+const process = require('process');
+const fs = require('fs');
+const path = require('path');
+
+const moduleDirPath = process.argv[2];
+
+let moduleDir = fs.opendirSync(moduleDirPath);
+
+const codeInventory = {};
+// codeInventory[system][code] = set("display1", "display2", ...)
+
+const allCodes = [];
+
+const codeDictionary = {};
+// codeDictionary[system][code] = "display to use"
+
+// systems to skip because tx.fhir.org doesn't know about them
+const SYSTEMS_TO_SKIP = ['NUBC', 'DICOM-DCM', 'DICOM-SOP'];
+
+// codes used in Synthea as placeholders that we know aren't real
+const PLACEHOLDER_CODES = ['999999',
+  "99999-0", "99999-1", "99999-2", "99999-3", "99999-4",
+  "99999-5", "99999-6", "99999-7", "99999-8", "99999-9",
+  "99999-10", "99999-11",
+  'X9999-0', 'X9999-1', 'X9999-2'];
+
+if (fs.existsSync('./code_dictionary.json')) {
+  const rawJSON = fs.readFileSync('./code_dictionary.json');
+  const loadedDictionary = JSON.parse(rawJSON);
+  Object.assign(codeDictionary, loadedDictionary);
+  console.log("Using previously saved ./code_dictionary.json")
+} else {
+  processFiles(moduleDir, moduleDirPath, inventoryAllCodes);
+  buildDictionary();
+  fs.writeFileSync('./code_dictionary.json', JSON.stringify(codeDictionary, null, 2));
+  console.log("Saved ./code_dictionary.json")
+  // re-open to re-iterate through
+  moduleDir = fs.opendirSync(moduleDirPath);
+}
+
+processFiles(moduleDir, moduleDirPath, checkAndUpdateAllCodes);
+
+function processFiles(dirEntry, parentPath, fileFunction) {
+  let fileInFolder = dirEntry.readSync();
+  while (fileInFolder != null) {
+    if(fileInFolder.isDirectory()) {
+      const newPath = path.join(parentPath, fileInFolder.name);
+      const subDir = fs.opendirSync(newPath);
+      processFiles(subDir, newPath, fileFunction);
+    } else if (fileInFolder.isFile() && fileInFolder.name.endsWith('.json')) {
+      const moduleJSONPath = path.join(parentPath, fileInFolder.name);
+      fileFunction(moduleJSONPath);
+    }
+    fileInFolder = dirEntry.readSync();
+  }
+}
+
+function inventoryAllCodes(moduleJSONPath) {
+  console.log(moduleJSONPath);
+  const rawJSON = fs.readFileSync(moduleJSONPath);
+  let module = JSON.parse(rawJSON);
+  
+  walkObject(module, inventoryCode);
+}
+
+function checkAndUpdateAllCodes(moduleJSONPath) {
+  console.log(moduleJSONPath);
+  const rawJSON = fs.readFileSync(moduleJSONPath);
+  let module = JSON.parse(rawJSON);
+  
+  walkObject(module, checkAndUpdateCode);
+
+  const updatedModuleJSON = JSON.stringify(module, null, 2);
+  fs.writeFileSync(moduleJSONPath, updatedModuleJSON);
+}
+
+/**
+ * Recursively iterate through the given object and
+ * apply the given function to any "code" objects.
+ * A "code" object is one that has fields "system", "code", and "display".
+ */
+function walkObject(object, codeFunction) {
+  if (Array.isArray(object)) {
+    object.forEach(o => walkObject(o, codeFunction));
+  } else if (typeof object === 'object' && object !== null) {
+    if (object.system && object.code && object.display) {
+      if (SYSTEMS_TO_SKIP.includes(object.system) || PLACEHOLDER_CODES.includes(object.code.toString())) {
+        return;
+      }
+      codeFunction(object);
+    } else {
+      for (const [key, value] of Object.entries(object)) {
+        walkObject(value, codeFunction);
+      }
+    }
+  }
+  // else, it's a null or primitive, nothing to do
+}
+
+/**
+ * Add the given code to the inventory.
+ */
+function inventoryCode(codeObj) {
+  let { system, code, display } = codeObj;
+  code = code.toString();
+
+  if (!codeInventory[system]) {
+    codeInventory[system] = {};
+  }
+  if (!codeInventory[system][code]) {
+    codeInventory[system][code] = new Set();
+    allCodes.push(codeObj);
+  }
+
+  codeInventory[system][code].add(display);
+}
+
+function buildDictionary() {
+  for (const codeObj of allCodes) {
+    let { system, code, display } = codeObj;
+    code = code.toString();
+    if (!codeDictionary[system]) {
+      codeDictionary[system] = {};
+    }
+
+    const body = requestBody(codeObj);
+    const VALIDATE_CODE_HEADERS = {
+      "Content-Type": "application/fhir+json",
+      "Accept": "application/fhir+json"
+    };
+    const res = fetch(
+        'http://tx.fhir.org/r4/CodeSystem/$validate-code?',
+        { 
+          method: 'POST', 
+          body: JSON.stringify(body, null, 2), 
+          headers: VALIDATE_CODE_HEADERS 
+        }).json();
+
+    const displayParam = res.parameter.find(p => p.name === 'display');
+    const success = res.parameter.find(p => p.name === 'result').valueBoolean;
+    if (success) {
+      // the current display may or may not be the singular best,
+      // but it is one of the allowed values.
+      // the "display" param contains the official best value
+      const bestDisplay = displayParam.valueString;
+
+      if (codeInventory[system][code].has(bestDisplay)) {
+        // we use the best display somewhere already, stick to it
+        codeDictionary[system][code] = bestDisplay;
+      } else {
+        // standardize to the current display
+        codeDictionary[system][code] = display;
+      }
+    } else {
+      if (displayParam) {
+        // the code is valid but the display is not allowed
+        // update the code to use the given display and
+        // store the given display going forward
+        codeDictionary[system][code] = displayParam.valueString;
+      } else {
+        handleErrorOrExit(body, res);
+      }
+    }
+  }
+}
+
+/**
+ * Construct the request body to validate the given code.
+ */
+function requestBody(codeObj) {
+  const coding = JSON.parse(JSON.stringify(codeObj)); // simple copy
+  coding.code = coding.code.toString();
+  switch (coding.system) {
+  case 'SNOMED-CT':
+    coding.system = 'http://snomed.info/sct';
+    break;
+  case 'LOINC':
+    coding.system = 'http://loinc.org';
+    break;
+  case 'RxNorm':
+    coding.system = 'http://www.nlm.nih.gov/research/umls/rxnorm';
+    break;
+  case 'CVX':
+    coding.system = 'http://hl7.org/fhir/sid/cvx';
+    break;
+
+  default:
+    console.log(`Unexpected code system ${coding.system} may not be supported by tx.fhir.org`);
+  }
+  return {
+    "resourceType": "Parameters",
+    "parameter": [
+      {
+        "name": "coding",
+        "valueCoding": coding
+      },
+      {
+        "name": "default-to-latest-version",
+        "valueBoolean": true
+      }
+    ]
+  }
+}
+
+/**
+ * Check whether the display on the given code is appropriate,
+ * and if not, update it.
+ */
+function checkAndUpdateCode(codeObj) {
+  let { system, code, display } = codeObj;
+  code = code.toString();
+  if (!codeDictionary[system][code]) {
+    // something went wrong in validating the code earlier,
+    // the log will show what it was
+    return;
+  }
+
+  // capitalization doesn't appear to matter, so only update a code
+  // if it differs in more than just caps
+  if (codeDictionary[system][code].toLowerCase() != display.toLowerCase()) {
+    console.log(`Updating "${display}" -> "${codeDictionary[system][code]}"`)
+    codeObj.display = codeDictionary[system][code];
+  }
+}
+
+/**
+ * Handle errors from the terminology service.
+ * "Unknown code" errors are expected so just print those out to the log.
+ * Anything else, print the request and response then exit.
+ */
+function handleErrorOrExit(body, res) {
+  const messageParam = res.parameter.find(p => p.name === 'message');
+  if (messageParam) {
+    const message = messageParam.valueString;
+
+    if (message.startsWith("Unable to find code ") 
+      || message.startsWith("Unknown Code '")) {
+      console.log(message);
+      return;
+    }
+  }
+  // something else went wrong. print message and stop
+  console.log("Error occurred.")
+  console.log("Request body:")
+  console.log(JSON.stringify(body, null, 2));
+  console.log("\nResponse:")
+  console.log(JSON.stringify(res, null, 2));
+  process.exit(1);
+}