From 3c68be79dc139788fb976a150088e4ea5946708b Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Thu, 9 Jun 2016 16:41:53 -0700
Subject: [PATCH] Throw an error in PID_autotune for E < -1

---
 Marlin/temperature.cpp | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index 61d9fe2e2f..bb6e1e6aff 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -206,15 +206,18 @@ unsigned char Temperature::soft_pwm[HOTENDS];
       next_auto_fan_check_ms = temp_ms + 2500UL;
     #endif
 
-    if (false
-      #if ENABLED(PIDTEMP)
-         || hotend >= HOTENDS
-      #else
-         || hotend >= 0
-      #endif
-      #if DISABLED(PIDTEMPBED)
-         || hotend < 0
-      #endif
+    if (hotend >=
+        #if ENABLED(PIDTEMP)
+          HOTENDS
+        #else
+          0
+        #endif
+      || hotend <
+        #if ENABLED(PIDTEMPBED)
+          -1
+        #else
+          0
+        #endif
     ) {
       SERIAL_ECHOLN(MSG_PID_BAD_EXTRUDER_NUM);
       return;